JP4315646B2 - Pneumatic tire - Google Patents

Description

【００３８】
テストの結果、実施例のものは、ビード部の耐久性を向上していることが確認できた。
【００３９】
【発明の効果】
以上説明したように、本発明の空気入りタイヤは、内圧充填前後のカーカスプライの形状変化を小さく抑えることによってタイヤのビード部などに局部的な内部歪が生じるのを防いでビード部の耐久性を向上しうる。
【図面の簡単な説明】
【図１】本発明の実施形態を示す正規内圧状態のタイヤ子午線断面図である。
【図２】本発明の実施形態を示す仮組み状態のタイヤ子午線断面図である。
【図３】図１のＡ−Ａ’断面図である。
【図４】図１のビード部を拡大して示す拡大断面図である。
【図５】本発明の他の実施形態を示す正規内圧状態のビード部の断面図である。
【図６】（Ａ）、（Ｂ）は、ビード部を拡大した部分断面図である。
【図７】比較例タイヤのビード部の拡大断面図である。
【図８】比較例タイヤのビード部の拡大断面図である。
【図９】比較例タイヤのビード部の拡大断面図である。
【符号の説明】
１ 空気入りタイヤ
２ トレッド部
３ サイドウォール部
４ ビード部
５ ビードコア
６ カーカス
６Ａ カーカスプライ
６ａ カーカスプライの本体部
６ｂ カーカスプライの折返し部
７ ベルト層
Ｈｃ カーカス高さ
Ｐ１ 正規内圧状態における０．２５倍高さ位置
Ｐ２ 仮組み状態における０．２５倍高さ位置[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire suitable for a heavy-duty vehicle capable of improving the durability of a bead portion.
[0002]
[Prior art and problems to be solved by the invention]
Heavy-duty pneumatic tires used in heavy-duty vehicles such as trucks and buses are used in severe conditions such as high internal pressure and high loads. For this reason, the improvement of durability, especially the improvement of durability of the bead part which is easy to generate | occur | produce damage has become an important subject.
[0003]
For example, in Japanese Patent No. 2816143, by providing a wedge-shaped rubber having a convex lens-shaped cross section disposed on the inner surface side of the carcass in the vicinity of the position corresponding to the height of the ply winding end measured from the rim diameter line on the carcass pass line. It has been proposed to increase the durability of the bead portion. In this proposal, by interposing the wedge rubber, an attempt is made to reduce the tensile strain at the outer end of the winding portion by generating a compressive stress in the rubber near the ply winding end.
[0004]
Japanese Patent Laid-Open No. 2001-80316 proposes further folding back the folded portion of the carcass ply along the outer surface of the bead core in the tire radial direction. In this proposal, it is expected that the input of compression and tension to the end of the folded portion of the carcass ply is reduced to prevent damage at the end.
[0005]
As a result of intensive studies, the inventors have found that it is effective to reduce the strain generated on the outer surface of the tire and the inside of the tire as one means for improving the durability of the bead portion. For this purpose, it has been found that it is effective to make the radius of curvature of the bead portion specific position of the carcass ply substantially equal when filling with normal internal pressure and when filling with internal pressure of 50 kPa, thereby completing the present invention. I came to let you.
[0006]
As described above, an object of the present invention is to provide a pneumatic tire that can improve the durability of the bead portion.
[0007]
[Means for Solving the Problems]
The invention according to claim 1 of the present invention is such that a body portion that extends from the tread portion to the bead core of the bead portion from the tread portion to the bead core is integrally provided with a folded portion that is folded from the inner side to the outer side in the tire axial direction. Carcass,
A belt layer arranged radially outside the carcass and inside the tread portion:
A pneumatic tire comprising a bead apex extending in a tapered shape from the bead core to the outside in the tire radial direction between the main body portion and the folded portion ,
In a no-load normal internal pressure state in which a normal rim is assembled and filled with a normal internal pressure, a distance of 0.25 times the carcass height Hc from the bead base line BL to the outermost position in the tire radial direction of the carcass is A radius of curvature R1 of the body portion of the carcass ply at a height of 0.25 times separated from the bead baseline;
In the unloaded temporary assembled state in which the rim is assembled to the regular rim and filled with 50 kPa, the curvature radius R2 of the main body portion of the carcass ply at the 0.25-fold height position is the 0.25-fold height. By increasing the thickness of the inner liner rubber centered on the position, or adding a rubber strip f etc. different from the inner liner and hitting it with the vulcanization bladder, both have a center inside the tire and (R1 / R2) is Ri 0.8 to 1.2 der,
In addition, the bead apex is formed in an arc shape in which the inner side surface 8i in the tire axial direction has a center in the tire axial direction along the main body portion 6a, and the outer side surface 8o in the tire axial direction is centered on the outer side in the tire axial direction. Formed in an arc shape having
The folded portion has a proximity portion in which the distance between the carcass cords between the folded portion and the main body portion is the smallest on the inner side in the tire radial direction from the outer end of the folded portion. The distance between the carcass cords gradually increases to the end .
[0008]
The invention according to claim 2 is characterized in that the folded portion extends beyond the outer end of the bead apex in the tire radial direction and the height h1 from the bead base line BL is 0.35 to 0.45 of the carcass height Hc. Double ,
The height ha of the bead apex from the bead base line BL is 0.13 to 0.17 times the carcass height Hc, and the turn-up portion is a distance between the carcass cords with the main body portion. 2. The pneumatic tire according to claim 1, further comprising: a proximity portion in which the minimum is the inner side in the tire radial direction from the outer end of the folded portion.
[0009]
According to a third aspect of the present invention, the bead portion is provided with a cord reinforcing layer extending along an outer side in the tire axial direction of the folded portion along the folded portion, and an outer end of the cord reinforcing layer in the tire radial direction. It shall be the being located in the tire radial direction inner side than 4mm than the outer end of the turnup portion.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 illustrates a tubeless heavy-duty radial tire 1 (hereinafter sometimes simply referred to as “tire 1”) used as a pneumatic tire for trucks, buses, and the like. The state of FIG. 1 shows a meridional section in a normal internal pressure state with no load, in which the tire 1 is mounted on the normal rim J (15 ° taper deep bottom rim) and the normal internal pressure is filled.
[0011]
In the present specification, the “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based. For example, a standard rim for JATMA and a “Design Rim” for TRA. Or, for ETRTO, "Measuring Rim". In addition, “regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. It is the maximum air pressure for JATMA and the table “TIRE LOAD LIMITS” for TRA. The maximum value described in “AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” for ETRTO, but 180 kPa when the tire is for passenger cars.
[0012]
In FIG. 1, a tire 1 is located at a tread portion 2, a pair of sidewall portions 3 extending inward in the tire radial direction from both ends thereof, and inner ends of the respective side wall portions 3 and seated on the regular rim J. And a bead portion 4 to be provided. Further, the tire 1 includes a body portion 6a that extends from the tread portion 2 through the side wall portion 3 to the bead core 5 of the bead portion 4, and a folded portion 6b that is folded back from the inner side in the tire axial direction to the outer side by the bead core 5. A carcass 6 including at least one carcass ply 6A is provided.
[0013]
The carcass ply 6A is composed of a ply in which a cord array in which carcass cords 6c are arranged is covered with a topping rubber 6g, as shown in FIG. 3 which is a cross section taken along line AA ′ of FIG. The carcass cord 6c is disposed so as to be inclined with respect to the tire equator C within an angle range of, for example, 70 to 90 °, more preferably 80 to 90 °. As the carcass cord 6c, a steel cord is employed in this example, but an organic fiber cord such as nylon, rayon, polyester, aromatic polyamide or the like can be used as necessary and according to the category of the tire. Note that the carcass 6 of the present embodiment is formed of a single carcass ply 6A in which a steel cord is inclined with respect to the tire equator C at an angle of approximately 90 °.
[0014]
A belt layer 7 is disposed outside the carcass 6 in the radial direction and inside the tread portion 2. In this example, the belt layer 7 includes the innermost belt ply 7A in which the steel cord is inclined with respect to the tire equator C at an angle of, for example, about 55 ± 10 °, and the steel cord is 30 ° or less with respect to the tire equator C. For example, a four-layer structure in which belt plies 7B, 7C, and 7D arranged at a small angle are overlapped by providing one or more places where the belt cords cross each other between the plies, for example. For the belt layer 7, other cord materials such as rayon, nylon, aromatic polyamide, and nylon can be used as necessary.
[0015]
In the bead portion 4, a bead apex 8 is disposed between the main body portion 6 a and the turn-up portion 6 b in a tapered shape extending outward from the bead core 5 in the tire radial direction. Bead apex 8, as shown enlarged in FIG. 4, the inner surface 8i of the tire axial direction, while being formed in an arc shape having a center in the tire axial direction inner side along the main body portion 6a, the tire axial direction The outer surface 8o is formed in an arc shape having a center on the outer side in the tire axial direction, and has a substantially drop-shaped cross section. The bead apex 8 is desirably formed of rubber having a JISA hardness of 60 to 99 °, more preferably 70 to 95 °, for example, so that the bending rigidity of the bead portion 4 can be sufficiently secured.
[0016]
The height ha of the bead apex 8 from the bead base line BL is, for example, 0.07 to 0.35 times the carcass height Hc, more preferably 0.07 to 0.20 times, and even more preferably 0.13 to 0.33. It is desirable to make it 0.17 times. The carcass height Hc is a height from the bead base line BL to the outermost position in the tire radial direction of the carcass 6 in the normal internal pressure state shown in FIG. If the height ha is less than 0.07 times the carcass height Hc, the tire tends to be difficult to manufacture. Conversely, if the height ha exceeds 0.35 times, the effect of improving the bead durability decreases and the tire weight decreases. Increase unnecessarily.
[0017]
As shown in FIG. 4, the folded portion 6b of the carcass ply 6A extends beyond the outer end 8t of the bead apex 8 outward in the tire radial direction. In this example, the outer end 6t of the folded portion 6b is located radially inward from the maximum width point M (shown in FIG. 1) that forms the maximum tire width position, and has a height h1 that has a relatively small amount of strain when loaded. Shows what The height h1 from the bead base line BL is set to a height of about 0.25 to 0.50 times, more preferably about 0.35 to 0.45 times the carcass height Hc. If the height h1 is less than 0.25 times the carcass height Hc, the shear stress generated between the main body portion 6a and the folded portion 6b cannot be reduced sufficiently, leading to a decrease in bead durability. On the other hand, if it exceeds 0.50 times, the bending rigidity of the bead portion 4 is excessively increased and the ride quality is liable to deteriorate.
[0018]
Further, in the normal internal pressure state shown in FIG. 1, the tire 1 has a distance 0.25 times the carcass height Hc (0.25 Hc) at a height position P1 that is 0.25 times apart from the bead base line BL. The radius of curvature R1 of the main body portion 6a of the carcass ply 6A and the 0.25-fold height position P2 in the unloaded temporary assembled state in which the regular rim J is assembled and filled with 50 kPa as shown in FIG. The ratio (R1 / R2) to the radius of curvature R2 of the main body portion 6a of the carcass ply 6A is 0.8 to 1.2, particularly preferably 0.9 to 1.1, more preferably 1.0. It is desirable to set it to -1.1. In this case, the carcass height Hc is determined in each of the normal internal pressure state and the temporarily assembled state, and accordingly, the 0.25-fold height positions P1 and P2 are also determined according to each carcass height Hc. The curvature radii R1 and R2 are specified by the center line of the thickness of the main body 6a of the carcass ply 6A.
[0019]
As described above, the tire 1 of the present invention limits the change in the radius of curvature of the main body portion 6a of the carcass ply 6A to a certain range at the 0.25-fold height positions P1 and P2 in each internal pressure state. The change in the radius of curvature of the main body 6a of the carcass ply 6A is reduced before and after filling.
[0020]
First, in the temporarily assembled state, it is necessary to uniquely determine the tire shape without applying as much tension as possible to the carcass cord 6c due to internal pressure. For this purpose, an internal pressure of 50 kPa is filled. If the internal pressure is less than 50 kPa, the shape is not uniquely determined even for the same tire. Conversely, if the internal pressure exceeds 50 kPa, the tension due to the internal pressure acts on the carcass cord 6c and the shape is likely to change.
[0021]
In the present invention, the radii of curvature R1 and R2 of the main body 6a of the carcass ply 6A at the 0.25-fold height positions P1 and P2 are targeted. As a result of various experiments by the inventors, it is particularly in the region of 0.13 to 0.38 times the carcass height Hc from the bead base line BL that particularly affects cracks and the like generated on the outer surface of the tire due to surface distortion. It turned out to be. Therefore, in the present invention, the curvature radii R1 and R2 at the 0.25-fold height positions P1 and P2, which are substantially the center value of this region, are defined so as not to change substantially.
[0022]
For example, as shown in FIG. 6 (A), the tire 1 having such a change in expansion increases the thickness F of the inner liner rubber i with the 0.25-fold height position P1 as the center. As shown in FIG. 6 (B), by adding a rubber strip f or the like different from the inner liner i, the main body 6a is greatly curved as compared with the conventional one, and a bladder (vulcanized bladder) during vulcanization molding is formed. the contact position) that can be produced by varying the conventional.
[0023]
Further, in the tire 1 according to the present embodiment, in the temporarily assembled state shown in FIG. 2, the main body portion 6a of the carcass ply 6A has a profile in the section from the outer end 7e of the belt layer 7 to the bead core 5, both inside the tire. Are formed by single or plural arcs having a center. When the internal pressure is filled and tension is applied to the carcass cord, the profile of the section usually deforms to approach a constant arc shape, but by providing the profile as described above from the temporarily assembled state, The curvature of the profile of the portion 6a is not reversed, and the carcass cord tension at the time of normal internal pressure filling is made uniform. This can reduce both the internal strain and the surface strain of the tire over the sidewall portion 3 and the bead portion 4, and can help to further improve the durability of the bead portion.
[0024]
The folded portion 6b extends outward in the tire radial direction along the outer side surface 8o of the bead apex 8, and between the folded portion 6b and the carcass cord 6c of the main body portion 6a in the vicinity of the outer end 8t of the bead apex 8. The proximity portion 10 has an inter-cord distance t (measured as shown in FIG. 3) which is a minimum value tmin. That is, the turn-up portion 6b has a distance between the carcass cords t with the main body portion 6a that is the smallest (the distance t is tmin). The proximity portion 10 is in the tire radial direction from the outer end 6t of the turn-up portion 6b. Have inside. The inter-cord distance (tmin) is, for example, preferably 0.15 to 4.5 times, more preferably 1.3 to 3.5 times the diameter D of the carcass cord 6c.
[0025]
In this way, by providing the proximity portion that minimizes the inter-cord distance t inside the outer end 6t of the folded portion 6b, the folded portion 6b approaches the neutral line of stress during tire deformation, and the folded portion The shear stress between 6b and the main body 6a is reduced, and damage such as cord breakage can be effectively suppressed. If the inter-cord distance tmin is less than 0.15 times the diameter D of the carcass cord 6c, the effect of relieving the shear stress is insufficient, and the carcass cord 6C may sometimes partially contact the cord. It can also cause looseness. On the other hand, if it exceeds 4.5 times, not only is it easy to cause breakage damage due to compression in the folded portion 6b, but it is also not preferable from the viewpoint of heat generation such as unnecessarily increasing the thickness of the bead portion 4. Such a proximity portion 10 may be local, for example, but the carcass cords of the main body portion 6a and the turn-up portion 6b are substantially reduced when the inter-cord distance t is continuous while forming a minimum value tmin. It is also preferable to form parallel regions G extending in parallel.
[0026]
When the parallel region G in which the adjacent portions X are continuous as described above is formed, the heat generation based on the shearing force acting on this portion can be effectively dispersed, and the effect of suppressing separation and the like that occurs in the vicinity of the outer end 8t of the bead apex 8 is suppressed. Therefore, the durability of the bead portion can be further improved.
[0027]
Further, in the present embodiment, as shown in an enlarged view in FIG. 4, the carcass ply main body portion 6 a and the folded portion 6 b are disposed outside the proximity portion 10 in the tire radial direction (in this example, following the parallel region G). A gradually increasing region Y is formed in which the inter-cord distance t gradually increases to the outer end 6t of the folded portion 6b. Such a gradually increasing region Y increases the thickness t of the inter-ply rubber with the main body 6a at the position of the outer end 6t of the folded portion 6b relative to the proximity portion 10 (in this example, the maximum value tmax). The separation at the outer end 6t of the folded portion 6b can be suppressed over a long period of time. On the other hand, the thickness of the inter-ply rubber between the main body portion 6a and the folded portion 6b is gradually reduced toward the outer end of the bead apex 8, so that the thickness at the position near the outer end 8t of the bead apex 8 is reduced. The rubber thickness between the plies can be made relatively small, and the occurrence of a separation starting point can be prevented also in this portion.
[0028]
FIG. 5 shows another embodiment of the present invention.
In the present embodiment, a structure in which one cord reinforcing layer 13 is disposed outside the carcass ply 6A of the bead portion 4 is shown. The cord reinforcing layer 13 includes an outer portion 14 extending outward in the tire radial direction along the outer side in the tire axial direction of the folded portion 6b, and an inner end side in the tire radial direction of the outer portion 14 and the tire radius of the bead core. And a winding portion 15 extending inward in the direction.
[0029]
For example, in the case of the heavy load tire of this example, the cord reinforcing layer 13 is preferably a steel cord, but other than this, an organic fiber cord such as an aromatic polyamide or an aliphatic polyamide can be appropriately employed. In the cord reinforcing layer 13, it is preferable that the cord is arranged at an angle of, for example, 30 to 90 ° with respect to the tire circumferential direction because the reinforcing effect is high. In this embodiment, the outer end 14t in the tire radial direction of the outer side portion 14 of the cord reinforcing layer 13 is separated from the outer end of the folded portion 6b by a distance T of 4 mm or more, more preferably 6 to 14 mm. The one located radially inward is shown. As a result, the outer end 6t of the folded portion 6b and the outer end 14t of the cord reinforcement layer 13 can be prevented from coming close to each other and separation or the like can be suppressed.
[0030]
On the other hand, the end portion 15t of the winding portion 15 of the cord reinforcing layer 13 may be terminated at the inner side of the bead core 5 as in this example, and the end portion of the winding portion 15 is indicated by a virtual line in FIG. The portion 15t may extend outward in the tire radial direction along the inner side in the tire axial direction of the main body portion 6a of the carcass ply 6A.
[0031]
As described above in detail, according to the present invention, the tire category is not limited to the above example, and can be applied to tires of various categories such as passenger cars, light trucks, and motorcycles.
[0032]
【Example】
A heavy-duty radial tire having a tire size of 11R22.5 (14PR) was prototyped and tested for durability. The test contents are as follows.
[0033]
(1) A bead durability test tire is assembled on a rim having a rim size of 8.25 × 22.5, filled with an internal pressure of 1000 kPa, and run on a drum tester at a speed of 20 km / H and a load of 88.3 kN. The travel distance until breakage was measured. The results were expressed as an index with Comparative Example 1 as 100. The larger the value, the better.
[0034]
(2) The road test tire was mounted on the front wheel of the truck for normal running, and the running distance when ozone cracks occurred on the outer surface of the bead portion was measured. The results were expressed as an index with Comparative Example 1 as 100. The larger the value, the better.
[0035]
The common specifications of tires are as follows.
<Carcass>
・ Ply number: 1
・ Cord: Steel (3 / 0.20mm + 7 / 0.23mm)
・ Cord angle: 90 ° (to tire equator)
<Belt layer>
・ Ply number: 4
・ Cord: Steel (1 × 5 × 0.38mm)
・ Number of cords to be driven: 26 / 5cm
・ Cord angle: + 50 °, + 18 °, -18 °, -18 ° (against tire equator)
[0036]
For those having a bead reinforcing layer, the following ply was used.
<Bead reinforcement layer>
・ Ply number: 1
・ Cord: Steel (3 / 0.20mm + 7 / 0.23mm)
・ Cord angle: 25 ° (to tire equator)
Table 1 shows the test results.
[0037]
[Table 1]

[0038]
As a result of the test, it was confirmed that the examples had improved durability of the bead portion.
[0039]
【The invention's effect】
As described above, the pneumatic tire according to the present invention prevents the occurrence of local internal distortion in the bead portion of the tire by suppressing the change in the shape of the carcass ply before and after filling with the internal pressure, thereby improving the durability of the bead portion. Can be improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a tire meridian in a normal internal pressure state showing an embodiment of the present invention.
FIG. 2 is a tire meridian cross-sectional view in a temporarily assembled state showing an embodiment of the present invention.
FIG. 3 is a cross-sectional view taken along the line AA ′ in FIG.
4 is an enlarged cross-sectional view showing a bead portion of FIG. 1 in an enlarged manner. FIG.
FIG. 5 is a cross-sectional view of a bead portion in a normal internal pressure state showing another embodiment of the present invention.
6A and 6B are partial cross-sectional views in which a bead portion is enlarged. FIG.
FIG. 7 is an enlarged cross-sectional view of a bead portion of a comparative tire.
FIG. 8 is an enlarged cross-sectional view of a bead portion of a comparative example tire.
FIG. 9 is an enlarged cross-sectional view of a bead portion of a comparative example tire.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 6A Carcass ply 6a Carcass ply main-body part 6b Carcass ply turn-up part 7 Belt layer Hc Carcass height P1 0.25 times high in a normal internal pressure state Position P2 0.25 times height position in temporarily assembled state

Claims (3)

A carcass integrally provided with a folded portion that is folded from the inner side to the outer side in the tire axial direction around the bead core on the main body portion from the tread portion through the sidewall portion to the bead core of the bead portion;
A belt layer arranged radially outside the carcass and inside the tread portion:
A pneumatic tire comprising a bead apex extending in a tapered shape from the bead core to the outside in the tire radial direction between the main body portion and the folded portion ,
In a no-load normal internal pressure state in which a normal rim is assembled and filled with a normal internal pressure, a distance of 0.25 times the carcass height Hc from the bead base line BL to the outermost position in the tire radial direction of the carcass is A radius of curvature R1 of the body portion of the carcass ply at a height of 0.25 times separated from the bead baseline;
In the unloaded temporary assembled state in which the rim is assembled to the regular rim and filled with 50 kPa, the curvature radius R2 of the main body portion of the carcass ply at the 0.25-fold height position is the 0.25-fold height. By increasing the thickness of the inner liner rubber centered on the position, or adding a rubber strip f etc. different from the inner liner and hitting it with the vulcanization bladder, both have a center inside the tire and (R1 / R2) is Ri 0.8 to 1.2 der,
In addition, the bead apex is formed in an arc shape in which the inner side surface 8i in the tire axial direction has a center in the tire axial direction along the main body portion 6a, and the outer side surface 8o in the tire axial direction is centered on the outer side in the tire axial direction. Formed in an arc shape having
The folded portion has a proximity portion in which the distance between the carcass cords between the folded portion and the main body portion is the smallest on the inner side in the tire radial direction from the outer end of the folded portion. A pneumatic tire characterized in that the distance between the carcass cords gradually increases to the end . The folded portion extends beyond the outer end of the bead apex in the tire radial direction and the height h1 from the bead base line BL is 0.35 to 0.45 times the carcass height Hc ,
The pneumatic tire according to claim 1, wherein a height ha of the bead apex from the bead base line BL is 0.13 to 0.17 times the carcass height Hc. The bead portion is provided with a cord reinforcement layer extending outside the folded portion along the tire axial direction along the folded portion,
3. The pneumatic tire according to claim 1, wherein an outer end of the cord reinforcing layer in the tire radial direction is positioned at least 4 mm inward in the tire radial direction from an outer end of the folded portion.

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