JP7139776B2 - pneumatic tire - Google Patents

Description

The present invention relates to a pneumatic tire comprising a carcass and apex rubber.

Patent Document 1 below discloses a first carcass ply in which a folded portion is formed by folding back each of a pair of bead cores, and a second carcass ply in which a terminal end is located outside each of the pair of bead cores in the axial direction of the tire. A pneumatic tire with a This type of pneumatic tire has great lateral rigidity and exhibits excellent durability.

Japanese Patent Application Laid-Open No. 2007-210363

In general, pneumatic tires have a small thickness of rubber covering the axially outer side of the bead core. For this reason, in the pneumatic tire described above, for example, when rubber flows during tire vulcanization, variations in rubber thickness increase on the outside of the bead core in the axial direction of the tire, resulting in a decrease in mass balance. There is a problem that the uniformity tends to deteriorate.

SUMMARY OF THE INVENTION The present invention has been devised in view of the problems described above, and a main object of the present invention is to provide a pneumatic tire capable of improving uniformity while maintaining durability performance.

The present invention is a pneumatic tire comprising a tread portion, a pair of bead portions in which bead cores are respectively embedded, and a carcass having a carcass cord extending between the pair of bead portions, wherein the carcass comprises the pair of A folded ply folded back from the inner side to the outer side in the axial direction around the bead core of the pair of bead cores, and a winding down ply having a terminal end radially outward of the outer surface of each of the pair of bead cores in the tire radial direction, The turnup ply has a body portion extending in a toroidal shape between the pair of bead cores and a pair of turnup portions folded around each of the pair of bead cores. An apex rubber extending radially inward and outward of the tire is disposed between the portion and the apex rubber, and the apex rubber is connected to an apex body extending in a tapered manner outward in the tire radial direction from the outer surface of the bead core, and the apex body, and , and a sheet-like strip apex having an outer end radially outward of the tire maximum width position, wherein the folded portion of the folded ply terminates radially outward of the strip apex.

In the pneumatic tire according to the present invention, it is preferable that the terminal end of the winding ply is positioned radially inward of the tire maximum width position.

In the pneumatic tire according to the present invention, it is desirable that the tire radial distance between the terminal end of the winding ply and the outer surface of the bead core is 10% to 20% of the tire section height.

In the pneumatic tire according to the present invention, it is desirable that the apex main body and the strip apex are in contact with each other over a length of 10 mm or more in the tire radial direction.

In the pneumatic tire according to the present invention, the apex body preferably has the same rubber composition as the strip apex.

In the pneumatic tire according to the present invention, the strip apex preferably has a rubber thickness of 0.5 to 1.0 mm.

In the pneumatic tire according to the present invention, it is preferable that the tire radial distance between the outer end of the strip apex and the tire maximum width position is 2% to 7% of the tire section height.

In the pneumatic tire of the present invention, the lowering ply of the carcass has a terminal end radially outward of the outer surface of the bead core in the tire radial direction. That is, the terminal end is arranged at a position where the rubber thickness is larger than the outer side of the bead core in the tire axial direction. As a result, for example, even if rubber flow occurs during vulcanization, variation in rubber thickness is small at the above position, and a decrease in mass balance is suppressed, so uniformity can be improved. In a pneumatic tire in which the terminal end of the hoisting ply is located radially outward of the outer surface of the bead core, the rigidity of the bead portion is reduced, and repeated strain during running is increased, resulting in deterioration in durability performance. Tend.

Therefore, in the pneumatic tire of the present invention, a sheet-shaped strip apex having an outer end radially outward of the tire maximum width position is disposed, and the folded portion of the folded ply of the carcass is positioned from the strip apex. also terminates radially outward of the tire. As a result, the flexural rigidity of the sidewall portion is increased, and the repeated strain during running can be alleviated. Further, in the pneumatic tire of the present invention, the strip apex is completely surrounded between the main body portion and the folded portion, so that the flexural rigidity of the sidewall portion is further enhanced. Therefore, high durability performance is maintained.

Therefore, the pneumatic tire of the present invention has improved uniformity while maintaining durability.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows an example of the pneumatic tire of this embodiment. 2 is an enlarged view of a bead portion and a sidewall portion of FIG. 1; FIG.

An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a meridian cross-sectional view of the right half of a pneumatic tire (hereinafter sometimes simply referred to as "tire") 1 of the present embodiment, including a tire rotating shaft (not shown) in a normal state. In this embodiment, a tire 1 for a small truck is shown as a preferred aspect. However, the present invention may be employed, for example, as the pneumatic tire 1 for passenger cars or for heavy loads.

The "normal state" is a no-load state in which the tire is mounted on a normal rim (not shown) and filled with a normal internal pressure. Hereinafter, unless otherwise specified, the dimensions of each portion of the tire are values measured in this normal state.

"Regular rim" refers to the rim defined for each tire in the standard system including the standard on which the tire is based. Then it is "Measuring Rim".

"Regular internal pressure" is the air pressure specified for each tire by each standard in the standard system including the standard that the tire is based on. AT VARIOUS COLD INFLATION PRESSURES" maximum value, ETRTO is "INFLATION PRESSURE".

The tire 1 of this embodiment includes a tread portion 2, a pair of sidewall portions 3 arranged on both sides thereof, and a bead portion arranged radially inward of the sidewall portion 3 and having a bead core 5 embedded therein. 4.

The bead core 5 of the present embodiment includes, for example, an outer surface 5a positioned furthest outward in the tire radial direction, and is formed with a substantially rectangular cross section. The bead core 5 is not limited to such an aspect, and may be formed in a hexagonal or circular cross section, for example. The bead core 5 is formed, for example, by winding a steel bead wire (not shown) in multiple rows and multiple stages.

In the present embodiment, the tire 1 includes a carcass 6 extending between the pair of bead portions 4, 4 and a belt layer 7 arranged outside the carcass 6 in the tire radial direction. In addition, the tire 1 includes, for example, a sidewall rubber 3G disposed axially outward of the carcass 6 at the sidewall portion 3, and a sidewall rubber 3G disposed axially outward of the carcass 6 at the bead portion 4. It includes a clinch rubber 4G connected to 3G.

The carcass 6 of this embodiment includes a turn-up ply 9 and a winding-down ply 10 . In FIG. 1, the winding-down ply 10 is shown colored for easy understanding. The turn-up ply 9 and the winding-down ply 10 have carcass cords (not shown) arranged at an angle of 75 to 90 degrees with respect to the tire equator C, for example. The turn-up ply 9 and the winding-down ply 10 are overlaid, for example, in a direction in which the carcass cords intersect each other. Carcass cords that can be used include, for example, organic fiber cords such as aromatic polyamide and rayon, and metal cords such as steel.

The belt layer 7 of this embodiment includes two belt plies 7A and 7B in the radial direction of the tire. The belt plies 7A and 7B are formed by arranging metal cords (not shown) such as steel cords at an angle of, for example, 15 to 40 degrees with respect to the tire circumferential direction. The belt layer 7 is not limited to being formed by such two belt plies 7A and 7B.

The turn-up ply 9 of the present embodiment is turned around the bead core 5 from the inside to the outside in the axial direction of the tire. In this embodiment, the turnup ply 9 includes a body portion 9a extending between the bead cores 5 in a toroidal shape, and a pair of turnup portions 9b connected to the body portion 9a and folded around the bead cores 5.

Although the turnup ply 9 is composed of one carcass ply in the present embodiment, it may be composed of, for example, two or more carcass plies.

The folded portion 9b includes, for example, an arc-shaped convex portion 11 that protrudes outward in the tire axial direction, and an arc-shaped concave portion 12 that is arranged radially inward of the convex portion 11 and concave inward in the tire axial direction. there is In this embodiment, the convex portion 11 is formed so as to include the tire maximum width position M in the tire radial direction. In this specification, the maximum tire width position M is the position where the body portion 9a of the turnup ply 9 protrudes most outward in the tire axial direction.

The convex portion 11 and the concave portion 12 are connected through an inflection point P in this embodiment. In this specification, the inflection point P has a tangent line at one point on the folded portion 9b, and the two portions of the folded portion 9b divided by the one point are on different sides of the tangent line at the one point. When there is, that one point is called an inflection point P.

The winding-down ply 10 of this embodiment extends in a toroidal shape between the bead portions 4 and 4 and is formed around the bead core 5 without being folded back. Such a lowering ply 10 can increase the rigidity of the sidewall portion 3 and the bead portion 4 together with the turn-up ply 9 .

The winding-down ply 10 of this embodiment has a terminal end 10e outside in the tire radial direction of the outer surface 5a of the bead core 5 in the tire radial direction. That is, the terminal end 10e is arranged at a position where the rubber thickness is larger than the outer side of the bead core 5 in the tire axial direction. As a result, for example, even if rubber flow occurs during vulcanization, at the above position, variations in rubber thickness of the clinch rubber 4G or the sidewall rubber 3G are small, and a decrease in mass balance is suppressed, thereby improving uniformity. can do. Further, the unwinding ply 10 is wound around the outer peripheral surface of a well-known cylindrical drum (not shown), for example, at the time of tire manufacture. At this time, an apex rubber 14, which will be described later, is arranged on the outside of the drum. The winding ply 10 of this embodiment has a smaller width than conventional winding plies. Therefore, the winding-down ply 10 is accurately wound along the tire circumference on the outer side of the apex rubber 14 arranged on the drum. Therefore, in the tire 1 of the present embodiment, the mass balance is ensured in the tire circumferential direction, so the uniformity is enhanced.

In this embodiment, the winding-down ply 10 is arranged outside the folded portion 9b in the axial direction of the tire. The winding-down ply 10 is not limited to such an aspect, and may be arranged, for example, on the axially outer side of the main body portion 9a and the inner side of the folded portion 9b in the tire axial direction.

The terminal end 10e of the lowering ply 10 is located axially inward of the tire maximum width position M in this embodiment. Since such a lowering ply 10 ensures the rigidity of the sidewall portion 3, high durability performance is maintained.

The terminal end 10e of the lowering ply 10 is positioned, for example, near the inflection point P of the folded portion 9b. The vicinity of the inflection point P is a region where a large thickness of the sidewall rubber 3G or the clinch rubber 4G is ensured on the axially outer side of the folded portion 9b. Therefore, for example, deterioration in mass balance due to rubber flow during vulcanization is suppressed. The vicinity of the inflection point P refers to an area within 10% of the tire cross-sectional height H centering on the inflection point P in the radial direction of the tire. The terminal end 10e is arranged inside the inflection point P in the tire radial direction in this embodiment. The tire section height H is the distance in the tire radial direction between the bead base line BL and the tire maximum diameter point in the tire 1 in the normal state.

The tire radial distance h1 between the terminal end 10e of the lowering ply 10 and the outer surface 5a of the bead core 5 is preferably 10% to 20% of the tire section height H, for example. In the case of the tire 1 for small trucks as in the present embodiment, if the terminal end 10e of the hoisting ply 10 is disposed at such a position, excessive increase in strain during running can be suppressed. The tire 1 in which the terminal end 10e of the lowering ply 10 is positioned radially outward of the outer surface 5a of the bead core 5 has greater repeated strain during running than the conventional tire 1. Durability tends to deteriorate.

In this embodiment, an apex rubber 14 extending radially inward and outward of the tire is arranged between the body portion 9a and the folded portion 9b of the folded ply 9. As shown in FIG.

FIG. 2 is an enlarged view of the sidewall portion 3 and the bead portion 4 of FIG. As shown in FIG. 2 , the apex rubber 14 of this embodiment includes an apex body 15 and a sheet-like strip apex 16 .

The apex main body 15 of this embodiment extends from the outer surface 5a of the bead core 5 to the outside in the tire radial direction in a tapered shape. The apex main body 15 is formed, for example, in a substantially triangular cross section.

The strip apex 16 of this embodiment continues to the apex main body 15 and has an outer end 16e outside the tire maximum width position M in the tire radial direction. In such a tire 1, the flexural rigidity of the sidewall portion 3 is enhanced, and thus repeated strain generated in the bead portion 4 during running can be alleviated. Therefore, deterioration of durability performance due to disposing the terminal end 10e of the lowering ply 10 on the outer side of the outer surface 5a in the tire radial direction is suppressed. In this embodiment, the strip apex 16 is formed in contact with the axially inner surface of the apex body 15 .

The tire radial distance h2 between the outer end 16e of the strip apex 16 and the tire maximum width position M is preferably 2% to 7% of the tire section height H. If the distance h2 is less than 2% of the tire section height H, the flexural rigidity of the sidewall portion 3 may decrease. When the distance h2 exceeds 7% of the tire section height H, the rubber volume of the sidewall rubber 3G near the tire maximum width position M where the rubber thickness becomes relatively small becomes small, and the rubber flows during vulcanization. There is a risk that the tire mass will fluctuate more and the uniformity will deteriorate.

In this embodiment, the turnup portion 9b of the turnup ply 9 has a terminal end 9t outside the strip apex 16 in the tire radial direction. As a result, the strip apex 16 is completely enclosed between the main body portion 9a and the folded portion 9b, so that the bending rigidity of the sidewall portion 3 is further enhanced. Therefore, high durability performance is maintained.

In order to improve uniformity while maintaining durability performance, the radial distance h3 between the terminal end 9t of the turnup portion 9b and the outer end 16e of the strip apex 16 is 2% to 7% of the tire section height H. It is desirable to have

The sheet-shaped strip apex 16 can be adhered with high accuracy even when it is wound around the outer side of the turn-up ply 9 wound around the outer peripheral surface of a well-known cylindrical drum (not shown) when the tire 1 is manufactured, for example. In order to exhibit such action effectively, the rubber thickness t of the strip apex 16 is desirably 0.5 to 1.0 mm.

The apex body 15 and the strip apex 16 preferably have a complex elastic modulus E* of, for example, 12-20 MPa. The apex body 15 and strip apex 16 preferably have a loss tangent tan δ of 0.10 to 0.20, for example. As a result, the adhesiveness to each rubber and the flexural rigidity of the sidewall portion 3 are enhanced in a well-balanced manner, and high durability performance is maintained.

In this specification, the complex elastic modulus E* and the loss tangent tan δ of rubber are values measured using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. under the following conditions in accordance with JIS-K6394.
Initial strain: 10%
Amplitude: ±2%
Frequency: 10Hz
Deformation mode: Tensile Measurement temperature: 70°C

The apex body 15 and strip apex 16 are constructed from the same rubber compound in this embodiment. As a result, the apex main body 15 and the strip apex 16 are integrally molded, so damage such as peeling is further suppressed.

In order to suppress separation between the apex body 15 and the strip apex 16, in this embodiment, the apex body 15 and the strip apex 16 are preferably in contact with each other over a length L1 of 10 mm or more in the tire radial direction.

Although the particularly preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the illustrated embodiments and can be modified in various ways.

Light truck tires having the basic structure shown in FIG. 1 were manufactured and tested for their durability performance and uniformity. The test method and main common specifications are as follows.
Tire size: 35 x 12.50R20
Rim size: 10.0JJ-20

<Durability>
Using a drum tester, each test tire was run and the running distance until damage occurred in the bead portion was measured. The results are shown as indices with Comparative Example 1 being 100. The larger the numerical value, the better the durability performance.
Internal pressure: 450kPa
Load: 16.77kN
Speed: 80km/h

<Uniformity>
Using a uniformity tester, the RFV of each sample tire was measured according to JASO C607:2000 "Uniformity test method for automobile tires". The results are shown as indices with Comparative Example 1 being 100. The smaller the numerical value, the better the uniformity.
Internal pressure: 450kPa
Load: 16.77kN
Speed: 60km/h
The results of the tests are shown in Table 1.
In addition, "A1" in Table 1 has h1/H of 10%,
"A2" has h1/H of -5%,
"A3" has h1/H of 25%,
"B1" has h2/H of 4%,
"B2" has h2/H of 10%,
"B3" has -4% h2/H,
"C1" has an h3/H of 4%,
"C2" has -4% h3/H,
"C3" is h3/H of 15%.
Comparative Example 1 is an aspect in which the terminal end of the lowering ply is located radially inward of the outer surface of the bead core.
Comparative Example 2 is an aspect in which the terminal end of the folded portion is positioned radially inward of the outer end of the strip apex.
Comparative Example 3 is an aspect in which the outer end of the strip apex is positioned radially inward of the tire maximum width position.

As a result of the test, it was confirmed that the example can exhibit excellent uniformity while maintaining durability performance as compared with the comparative example. In addition, tests were conducted using tires in which the rubber thickness of the strip apex was varied within the preferred range, and similar results were obtained.

1 pneumatic tire 2 tread portion 3 bead portion 5 bead core 5a outer surface 6 carcass 9 turn-up ply 9a main body portion 9b turn-up portion 10 lowering ply 10e terminal end 14 apex rubber 15 apex main body 16 strip apex M tire maximum width position

Claims (6)

A pneumatic tire comprising a tread portion, a pair of bead portions in which bead cores are respectively embedded, and a carcass having a carcass cord extending between the pair of bead portions,
The carcass includes a folded ply folded back around the pair of bead cores from the inner side to the outer side in the tire axial direction, and a winding having a terminal end outside the outer surface in the tire radial direction of each of the pair of bead cores in the tire radial direction. a lowering ply;
The turn-up ply has a body portion extending in a toroidal shape between the pair of bead cores, and a pair of turn-up portions folded around each of the pair of bead cores,
An apex rubber extending radially inward and outward of the tire is disposed between the body portion and the folded portion of the folded ply,
The apex rubber includes an apex body extending taperingly outward in the tire radial direction from the outer surface of the bead core, and a sheet-like sheet-like body continuous with the apex body and having an outer end radially outward of the maximum width position of the tire. including Strip Apex and
The folded portion of the folded ply terminates outside the strip apex in the tire radial direction ,
The pneumatic tire is for small trucks, passenger cars or heavy loads,
The tire radial distance between the outer edge of the strip apex and the tire maximum width position is 2% to 7% of the tire section height.
pneumatic tires. 2. The pneumatic tire according to claim 1, wherein said terminal end of said lowering ply is positioned radially inward of the tire maximum width position. The pneumatic tire according to claim 1 or 2, wherein the tire radial distance between the terminal ends of the winding plies and the outer surface of the bead core is 10% to 20% of the tire section height. The pneumatic tire according to any one of claims 1 to 3, wherein said apex main body and said strip apex are in contact with each other over a length of 10 mm or more in the tire radial direction. 5. The pneumatic tire of any preceding claim, wherein the apex body is of the same rubber formulation as the strip apex. The pneumatic tire according to any one of claims 1 to 5, wherein the strip apex has a rubber thickness of 0.5 to 1.0 mm.

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