JP4458628B2 - Pneumatic tire - Google Patents

Description

【００２１】
表１によれば、実施例タイヤはいずれも、従来タイヤおよび比較タイヤのそれぞれに比して、ビード部耐久性を大きくに向上させ得ることが解る。
【００２２】
【発明の効果】
かくしてこの発明によれば、とくに、巻き回し部のカーカスコードの、ビードベース側に向くビードコア表面上での延在部分の、ビードコア中心軸線に対する傾き角を６０°以上９０°未満とするとともに、カーカスプライの巻き回し方向に隣接するビードコア表面上での延在部分の、同様の傾き角を、上記傾き角より大きくし、そして、両傾き角の差を２０°以下とすることにより、タイヤビード部の耐久性を大きく向上させることができる。
【図面の簡単な説明】
【図１】 この発明の実施形態を示す要部横断面図である。
【図２】 他の実施形態を示す要部横断面図である。
【図３】 カーカスプライの側部部分巻き回し部でのカーカスコードの延在態様を例示する説明図である。
【図４】 提案技術におけるカーカスコードの延在態様を示す図３と同様の図である。
【図５】 従来タイヤのビード部構造を示す横断面図である。
１ トレッド部
２ サイドウォール部
３ ビード部
３ａ ビードベース
４ ビードコア
４ａ，４ｂ ビードコア表面
５ カーカスプライ
６ 側部部分
７ 巻き回し部
８ ワイヤチェーファ
９ ビードフィラ
１０ カーカスコード
１０ａ，１０ｂ 延在部分
α，β 傾き角
Ｃ ビードコア中心軸線
ｂ１，ｂ２，ｂ３ 折曲げ加工部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire, in particular, a separation at a winding end caused by fixing a side portion of a carcass ply wound around a bead core disposed in a tire bead portion by winding it up outward in the tire radial direction. And a bead portion structure that sufficiently prevents the carcass cord from being pulled out.
[0002]
[Prior art]
In a general pneumatic tire, for example, a heavy-duty pneumatic radial tire, the side portion of the carcass ply is arranged around the bead core in the tire radial direction in order to prevent the carcass cord from being pulled out when the tire rolls. However, according to this, it is unavoidable that separation occurs at the winding end of the carcass ply. Therefore, in recent years, it has been disclosed in JP-A-11-32244. As described above, the carcass includes a wound carcass ply that has a winding portion that is substantially wound around the bead core and has an end portion that terminates around the bead core, thereby reducing the weight of the tire. Techniques for improving bead durability have been proposed.
[0003]
[Problems to be solved by the invention]
However, this proposed technique is related to the tire circumferential direction line of the portion passing through the outer peripheral surface of the bead core with respect to the relative relationship between the portion passing through the outer peripheral surface of the bead core and the portion passing through the inner peripheral surface of the bead core. When the angle θ1 formed is 30 to 90 ° and the angle θ2 formed with the tire circumferential direction line passing through the inner peripheral surface of the bead core is 30 to 90 °, and these angles θ1 and θ2 are smaller than 90 ° The portions passing through the outer peripheral surface and the inner peripheral surface of the bead core are arranged so as to cross each other. Under such an arrangement, the outer periphery of the bead core 32 of the carcass cord 31 as shown in FIG. Each of the portion 31a passing through the surface and the portion 31b passing through the inner peripheral surface thereof extends in different directions from each other. 31a has a substantially different extension angle in the circumferential direction with respect to the main body portion extending in the radial direction of the carcass cord 31, and therefore, under the tendency of straightening of the carcass cord 31 due to the action of tension on the carcass cord 31. Further, the circumferential deformation or displacement generated in the winding portion increases, and as a result, the circumferential strain at the ply end increases, and the tension acting on the carcass cord 31 is not evenly distributed over the entire length of the winding portion. The problem that the durability of the tire bead portion cannot be substantially improved due to the risk of fatigue fracture of the cord 31 due to repeated stress concentration due to rolling of the tire, etc. was there.
[0004]
The present invention has a problem of solving such problems of the proposed technique, and the object of the present invention is to make the contact length of the carcass cord with the bead core as long as possible, Assuming that the carcass cord pull-out resistance is sufficiently enhanced, the carcass cord is sufficiently prevented from causing circumferential deformation or displacement due to the large angle change as described above, and to the carcass cord. An object of the present invention is to provide a pneumatic tire in which bead portion durability is greatly improved by effectively preventing stress concentration due to the action of tension.
[0005]
[Means for Solving the Problems]
The pneumatic tire according to the present invention extends in a toroidal manner between ring-shaped bead cores arranged in the bead portion, and each side portion around the bead core having a polygonal cross-sectional shape in the tire width direction. Comprising at least one carcass ply with a winding part wound from the inside to the outside or from the outside to the inside,
The inclination angle of the carcass cord of the winding portion on the bead core surface facing the bead base, that is, the portion extending in the direction crossing the inner peripheral surface of the bead core, with respect to the bead core central axis, more specifically, The inclination angle (α) at the center of the surface is in the range of 60 ° to less than 90 °, more preferably in the range of 70 ° to less than 90 °, and in the winding direction of the carcass ply with respect to the bead core surface. The same inclination angle (β) of the extended portion on the adjacent bead core surface is made larger than the inclination angle (α), and the difference (β−α) between these inclination angles is 20 ° or less, more preferably The range is 17 ° or less.
[0006]
In this tire, the side portion of the carcass ply is wound around the bead core, and the high winding portion radially outward is removed from the side portion, thereby generating separation to the carcass ply winding end, and consequently In addition to effectively preventing the occurrence and growth of bead cracks due to the separation, the angle of inclination of the extended portion of the bead core on the inner peripheral surface of the carcass cord wound around the bead core By making (α) smaller than the inclination angle (β) on the surface adjacent to it and making the difference (β−α) between these inclination angles 20 ° or less, a long cord around the bead core The carcass cord is secured under a relatively small angle change in the extending direction of the carcass cord while ensuring a pass and sufficiently enhancing the resistance of the carcass cord to pull out. Without the suspicion of damage of the bead portion durability as described above due to the sudden angle change of the carcass ply, the extending direction of the carcass ply at the end of the carcass ply can be made sufficiently close to that of the carcass ply main body part, For this reason, it is possible to suppress circumferential deformation or displacement in the winding portion of the carcass cord, to reduce distortion at the ply end, and to sufficiently prevent local stress concentration on the carcass cord. it can.
[0007]
Further, in this tire, by setting the inclination angle (α) of the extending portion on the inner peripheral surface of the bead core in a range of 60 ° or more and less than 90 °, the circumferential direction of the winding portion of the carcass cord in the radial tire is increased. Strain at the end of the carcass ply can be reduced by suppressing deformation or displacement.
[0008]
In other words, if it is less than 60 °, the distortion of the carcass ply end due to the separation of the path from the base of the entrainment to the tip cannot be sufficiently reduced.
This also applies to the case where the difference between both inclination angles (β−α) is a value exceeding 20 °.
[0009]
In such a tire, when the winding portion is provided with three or more bent portions located corresponding to the corner portions of the bead core, the carcass cord is wound along the outer contour of the bead core accurately. In addition, the springback of the carcass cord can be advantageously prevented, and the carcass cord can be more effectively prevented from being pulled out.
[0010]
Here, when the wire chafer is disposed around the bead core so as to circumscribe the carcass ply, the reinforcement effect of the bead portion can be improved.
[0011]
In addition, when a bead filler is disposed from the outer peripheral side of the winding portion of the carcass ply to the sidewall portion, the winding portion is pressed down by the bead filler to effectively prevent unexpected loosening of the winding portion. can do.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below based on the drawings.
FIG. 1 is a cross-sectional view of a principal part showing an embodiment of a heavy-duty pneumatic radial tire in a posture in which a rim-assembled tire is filled with air pressure, in which 1 is a tread portion and 2 is a tread portion 1. Side wall portions extending radially inward from the side portions, and 3 indicates a bead portion provided continuously on the inner peripheral side of the side wall portion 2, and each bead portion 3 is embedded and disposed therein. As a whole, it has a ring shape, and includes a bead core 4 having a substantially hexagonal cross section.
[0013]
Further, here, the carcass ply 5 is extended toroidally between the bead cores 4, and at least one side portion 6 of the carcass ply 5 is wound around the bead core 4 so as to follow the peripheral surface of the bead core 4. And extending around the bead core 4, thereby removing from the side portion 6 of the carcass ply 5 a high outwardly raised portion in the radial direction.
[0014]
In addition, in the place shown in FIG. 1, although such winding of the carcass ply side portion 6 is performed from the inner side to the outer side in the tire width direction, the winding is performed as shown in FIG. It can also be performed from the outside in the width direction to the inside.
[0015]
The winding part 7 formed in this way can realize a sufficiently strong fixing of the side part 6 and, consequently, the carcass ply 5 to the bead core 4, which is, for example, the winding part 7. Bending portions b1, b2, and b3 are provided at least at one location corresponding to the corners of the bead core 4 so as to be wound around the bead core 4, thereby ensuring the reliable maintenance of the winding posture of the winding portion 7. It is especially effective in cases.
[0016]
1 and 2, 8 is a wire chafer arranged around the bead core 4 and circumscribed to the carcass ply 5, and 9 is from the outer peripheral side of the winding portion 7 to the sidewall portion 2. Each bead filler is disposed and restrains the winding portion 7 in the radial direction, and R denotes a rim assembled to the tire.
[0017]
In this tire, as shown in an example in FIG. 3, the carcass cord 10 constituting the carcass ply 5 is disposed on the bead base 3 a side of the ring-shaped bead core 4 at the winding portion 7 provided on the side portion 6. The inclination angle α on the acute angle side of the extending portion 10a on the facing surface 4a with respect to the bead core central axis C is in the range of 60 ° or more and less than 90 °, more preferably 70 to less than 90 °, and the surface 4a On the other hand, the same inclination angle of the extended portion 10b on the bead core surface 4b adjacent in the winding direction of the carcass ply 5, that is, the inclination angle β in the development view of the bead core surface shown in FIG. The inclination angle α is set larger than that, and the difference (β−α) between both inclination angles is set to 20 ° or less, more preferably 17 ° or less.
[0018]
According to the tire configured as described above, the angular change in the circumferential direction at the winding portion 7 of the carcass cord 10 is reduced, and the extending direction of the carcass cord 10 at the end portion of the carcass ply is set in the carcass ply. The ply body portion can be aligned with that of the ply body portion, and therefore, the durability of the bead portion 3 is effectively suppressed by suppressing the deformation or displacement of the wound portion 7 in the circumferential direction due to the action of the tension on the carcass cord 10. Can be improved.
As mentioned above, although embodiment of this invention was described based on the place shown in drawing, the cross-sectional shape of the bead core 4 can also be made into a square, a pentagon, etc. FIG.
[0019]
【Example】
Below, each bead part endurance test of an example tire, a conventional tire, and a comparison tire is described.
Here, the bead portion durability is a heavy load radial tire having a size of 315/60 R22.5, and Example tires 1 to 3 and comparative tires 1 and 2 having the bead portion structure shown in FIGS. 1 and 3, and When a 9.00 × 22.5 rim is assembled to each of the conventional tires having the bead structure shown in FIG. 5 and the filling air pressure is set to 900 kPa, a load corresponding to twice the maximum load capacity acts. In the drum running test, it was obtained by measuring the running distance until the running became impossible due to a bead part failure (separation at the end of the carcass ply or the wire chafer), and the index was evaluated using the conventional tire as a control.
[0020]
The results are shown in Table 1.
It should be noted that the larger the index value, the better the result.
[Table 1]

[0021]
According to Table 1, it can be seen that all of the example tires can greatly improve the bead durability as compared with the conventional tire and the comparative tire.
[0022]
【The invention's effect】
Thus, according to the present invention, in particular, the inclination angle of the extended portion of the carcass cord of the winding portion on the bead core surface facing the bead base with respect to the bead core central axis is set to 60 ° or more and less than 90 °. By making the same inclination angle of the extended part on the bead core surface adjacent to the winding direction of the ply larger than the above inclination angle and making the difference between the two inclination angles 20 ° or less, the tire bead portion The durability of can be greatly improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a main part showing an embodiment of the present invention.
FIG. 2 is a cross-sectional view of a main part showing another embodiment.
FIG. 3 is an explanatory view illustrating an extending aspect of a carcass cord at a side part winding portion of a carcass ply.
FIG. 4 is a view similar to FIG. 3 showing a carcass cord extending manner in the proposed technique.
FIG. 5 is a cross-sectional view showing a bead portion structure of a conventional tire.
DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 3a Bead base 4 Bead core 4a, 4b Bead core surface 5 Carcass ply 6 Side part 7 Winding part 8 Wire chafer 9 Bead filler 10 Carcass cord 10a, 10b Extension part alpha, beta inclination Angle C Bead core center axis b1, b2, b3 Bending part

Claims (6)

It extends in a toroidal manner between ring-shaped bead cores arranged in the bead portion, and each side portion is arranged around the bead core having a polygonal cross-sectional shape along the circumferential surface in the tire width direction. In a pneumatic tire comprising at least one carcass ply having a winding portion wound from the inside to the outside or from the outside to the inside,
The inclination angle (α) of the extended portion of the carcass cord of the winding portion on the bead core surface facing the bead base side with respect to the bead core central axis is in the range of 60 ° or more and less than 90 °, and the bead core surface On the other hand, the same inclination angle (β) of the extended portion on the surface of the bead core adjacent in the winding direction of the carcass ply is made larger than the inclination angle (α), and the difference between these inclination angles (β−α) Is a pneumatic tire having an angle of 20 ° or less. 2. The pneumatic according to claim 1, wherein an inclination angle (α) of the extended portion of the carcass cord of the winding portion on the surface of the bead core facing the bead base with respect to the bead core central axis is 70 ° or more and less than 90 °. tire.   The pneumatic tire according to claim 1 or 2, wherein a difference between the respective inclination angles (β-α) is 17 ° or less. The pneumatic tire according to any one of claims 1 to 3, wherein the wound portion is provided with three or more bent portions positioned corresponding to the corners of the bead core.   The pneumatic tire according to claim 1 or 4, wherein a wire chafer is disposed around the bead core so as to circumscribe the carcass ply. The pneumatic tire according to claim 1, 4 or 5 and comprising disposed bead filler from the outer peripheral side of the winding turning portion of the carcass ply toward the sidewall portion.

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