JP4855562B2 - Pneumatic tire - Google Patents

Description

【００２２】
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向上させ得ることが解る。
【００２３】
【発明の効果】
かくしてこの発明によれば、とくに、巻き回し部で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鋭角側の傾き角αを６２°以上８０°以下の範囲とし、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に対して、カーカスプライの巻き回し方向前方側に一の表面を隔てた離隔表面上での延在部分の、ビードコア中心軸線に対する鋭角側の傾き角βと、上記鋭角側の傾き角αとの差を１８°以下とし、さらに、前記カーカスコードの両延在部分のそれぞれの、ビードコアの横断面に対する延在方向を相互に逆とすることにより、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】 この発明の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の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，４ｃ 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，１０ｃ カーカスコードの延在部分
α，β 鋭角側の傾き角
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 carcass ply side portion wound around a bead core disposed in a tire bead portion. The present invention relates to a bead portion structure that prevents separation and 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 whose end ends 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 ° In this case, 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 bead core 32 of the carcass cord 31 is arranged as shown in FIG. Each of the portion 31a passing through the outer peripheral surface and the portion 31b passing through the inner peripheral surface thereof extend in different directions from each other. The minute 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, so that the carcass cord 31 is straightened by the action of tension on the carcass cord 31 in the product tire. Under the tendency, 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 evenly distributed over the entire length. This is likely to cause local stress concentration, and the repeated stress concentration caused by rolling of the tire increases the risk of fatigue breakage of the cord 31, resulting in substantial improvement in durability of the tire bead portion. There was a problem of not getting.
[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]
In the pneumatic tire of the present invention, at least one carcass ply extends in a toroidal manner between ring-shaped bead cores arranged in the bead portion, and each side portion of the carcass ply has six cross-sectional shapes. The bead base side of the carcass cord at the winding part around the bead core that forms a polygon more than a square, is wound along the circumference from the inside to the outside in the tire width direction or from the outside to the inside. The inclination angle α on the acute angle side with respect to the bead core central axis of the extended portion on the bead core surface facing the bead is in the range of 62 ° ≦ α ≦ 80 °, and the bead core surface of the carcass cord facing the bead base side, Inclination angle β on the acute angle side with respect to the bead core central axis of the extending portion on the separation surface with one surface separated forward in the winding direction of the carcass ply, and the acute angle side The difference from the inclination angle α of the carcass cord is | α−β | ≦ 18 °, and each of the extending portions around the ring-shaped bead core of the carcass cord extends toward the front side in the winding direction of the carcass ply. The directions are opposite to each other with respect to the cross-section of the bead core .
[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 The bead core central axis of the extended portion of the carcass cord on the bead base side facing the bead base as well as effectively preventing the occurrence and growth of bead cracks due to the separation. By setting the inclination angle α on the acute angle side to the range of 62 ° or more and 80 ° or less, the deformation or displacement in the circumferential direction of the wound portion of the carcass cord in the radial tire is suppressed, and the distortion at the end of the carcass ply is reduced. Can be reduced. If it is less than 60 °, the distortion at the end of the carcass ply cannot be reduced sufficiently.
[0007]
Also, in this tire, an acute angle with respect to the bead core central axis of the extended portion of the carcass cord on the separated surface that is separated from one surface on the front side in the winding direction of the carcass ply with respect to the bead core surface facing the bead base side By making the difference between the inclination angle β on the side and the inclination angle α on the acute angle side 18 ° or less, a long cord path around the bead core is secured, and the pullout resistance of the carcass cord is sufficiently enhanced. It should be noted that the carcass ply end portion has a relatively small change in the direction in which the carcass cord extends, and the bead portion durability is not damaged as described above due to the sudden change in the angle of the carcass cord. The carcass cord extension direction of the carcass ply can be made sufficiently close to that of the carcass ply main body, and this prevents the circumferential deformation or displacement of the carcass cord winding portion. Therefore, the strain at the ply end can be reduced, and the local stress concentration on the carcass cord can be sufficiently prevented. When the difference between the two inclination angles is larger than 20 °, the carcass cord is not evenly tensioned, and the extended portion of the carcass cord on the bead core surface facing the bead base side and the extended portion As a result, a large force is applied to either the extended portion of the carcass cord on the separation surface that is separated from the front surface in the winding direction of the carcass ply, and the carcass cord is bent at the position where the carcass cord is bent. There are defects such as breakage.
[0008]
In such a tire, the extending direction toward the front side in the winding direction of the carcass ply of each of the extending portions around the ring-shaped bead core of the carcass cord is opposite to the cross-section of the bead core. As a result, circumferential deformation or displacement generated in the winding portion of the carcass ply is prevented, and the durability of the tire bead portion is substantially improved. That is, unless the extending directions of the two extending portions of the carcass cord with respect to the cross-section of the bead core are opposite to each other, a circumferential deformation or displacement occurs in the winding portion of the carcass ply. When the circumferential strain at the ply end increases, if the stress concentration repeatedly acts due to rolling of the tire under this condition, the risk of fatigue breakage of the carcass cord increases, and the durability of the tire bead portion is substantially reduced. Improvement cannot be realized.
[0009]
Also, here, when the winding part is provided with three or more bent parts located corresponding to the corners 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]
When the wire chafer is disposed around the bead core so as to circumscribe the carcass ply, deformation of the carcass cord at the time of load can be suppressed and the durability of the carcass cord 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 slack 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 inward in the radial direction from the side portions, and 3 denotes a bead portion provided continuously on the inner peripheral side of the side wall portion 2.
[0013]
Here, each bead portion 3 is formed in a ring shape as a whole, and in the figure, a bead core 4 having a substantially hexagonal cross section is embedded and arranged, and at least one carcass ply 5 is extended between the bead cores 4 in a toroidal manner. And the side portion 6 of the carcass ply 5 is wound around the bead core 4 so as to extend along the peripheral surface of the bead core 4 and is finished around the bead core 4. From the side part 6 of the ply 5, a high winding part radially outward is removed.
[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 parts b1, b2, b3 are provided in at least one place 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 part 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 extending portion 10a on the surface 4a facing, in a range of acute side tilt angle α of 62 ° 80 ° or more or less of a relative bead core center axis C, also of the carcass cord 10, the bead core surface facing the bead base 3a side 4a, the inclination angle β on the acute angle side with respect to the bead core central axis C of the extending portion 10c on the separation surface 4c separating the one surface 4b on the front side in the winding direction of the carcass ply 5, and the acute angle side and the difference of 18 ° in the following range of the inclination angle α of.
[0018]
The inclination angle of the main body portion of the carcass cord 10 on the acute angle side with respect to the bead core central axis C is set to 70 ° to 90 °, and the ring-shaped bead core of the carcass cord 10 is shown by a solid line or a chain line in FIG. The extending directions of the two extending portions 10a and 10c around 4 with respect to the cross section of the bead core 4 are opposite to each other.
[0019]
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. Has been described above based have shown an embodiment of the invention with reference to the drawings, the cross-sectional shape of the bead core 4 may be a polygonal hexagon above.
[0020]
【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 the tires 1 to 4 and comparative tires 1 and 2 having the bead portion structure shown in FIG. 1 and FIG. 5, a 9.00 × 22.5 rim is assembled to each of the conventional tires having the bead portion structure shown in FIG. 5 and a load corresponding to 185% of the maximum load capacity is obtained at a filling air pressure of 900 kPa. In the drum running test, the speed was set to 60 km / h, and the conventional tire was determined by measuring the running distance until the bead portion failed (carcass ply end or wire chafer end separation, etc.). The index was evaluated as a control.
[0021]
The results are shown in Table 1.
It should be noted that the larger the index value, the better the result.
[Table 1]

[0022]
According to Table 1, it can be seen that any of the example tires can significantly improve the bead durability as compared with the conventional tire and the comparative tire.
[0023]
【The invention's effect】
Thus, according to the present invention, in particular, the inclination angle α on the acute angle side with respect to the bead core central axis of the extended portion of the carcass cord in the winding portion on the bead core surface facing the bead base side is 62 ° or more and 80 ° or less. A sharp angle side with respect to the bead core central axis of the carcass cord extending from the bead core surface of the carcass cord facing the bead base side on the surface separated from the front surface in the winding direction of the carcass ply. And the acute angle side inclination angle α is 18 ° or less, and the extending directions of the two extending portions of the carcass cord with respect to the cross-section of the bead core are opposite to each other. By doing so, the durability of the tire bead portion 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 an essential part showing another embodiment of the present invention.
FIG. 3 is an explanatory view exemplifying an extending aspect of a carcass cord at a winding portion of a side portion of the carcass ply.
FIG. 4 is a diagram showing how carcass cords are extended 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, 4c Bead core surface 5 Carcass ply 6 Side part 7 Winding part 8 Wire chafer 9 Bead filler 10 Carcass cord 10a, 10c Carcass cord extension Part α, β Acute angle C bead core central axis b1, b2, b3 Bending part

Claims (4)

Between the ring-shaped bead cores arranged in the bead portion, at least one carcass ply extends in a toroidal shape, and each side portion of the carcass ply has a polygonal cross-sectional shape that is a hexagon or more. In a pneumatic tire that is wound around the tire from the inside to the outside in the tire width direction along the circumferential surface or from the outside to the inside,
An inclination angle α on the acute angle side with respect to the bead core central axis of the extended portion of the carcass cord at the winding portion on the bead core surface facing the bead base side,
62 ° ≦ α ≦ 80 °
A sharp angle side with respect to the bead core central axis of the carcass cord extending from the bead core surface of the carcass cord facing the bead base side on the surface separated from the front surface in the winding direction of the carcass ply. The difference between the inclination angle β and the inclination angle α on the acute angle side,
| Α-β | ≦ 18 °
age,
A pneumatic tire in which the extending directions toward the front side in the winding direction of the carcass ply of each of the extending portions around the ring-shaped bead core of the carcass cord are opposite to each other with respect to the cross section of the bead core .   The pneumatic tire according to claim 1, 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 2, wherein a wire chafer is disposed around the bead core so as to circumscribe the carcass ply.   The pneumatic tire according to any one of claims 1 to 3, wherein a bead filler is disposed from an outer peripheral side of a winding portion of the carcass ply to a sidewall portion.

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