JP4467151B2 - Pneumatic tire - Google Patents

Description

【００２４】
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ることができ、また、コードの耐引き抜け性を十分に高め得ることが解る。
【００２５】
【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に対して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、ビードコア中心軸線に対する傾き角を７０°以上９０°未満とするとともに、その表面に対してカーカスプライの巻き回し方向にさらに隣接するビードコア表面上での延在部分の、同様の傾き角と、上記傾き角との差を一定の範囲に特定することにより、カーカスコードの耐引き抜け性を十分に確保して、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】 この発明の実施の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（ａ）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，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，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 parts 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 extends in different directions, and these extended portions, particularly among them. The minute portion 31a has a substantially different circumferential extension angle with respect to the main body portion of the carcass cord 31 extending in the radial direction, and therefore, the carcass cord 31 tends to be straightened by the action of tension on the carcass cord 31. Below, 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. In particular, local stress concentration is likely to occur, and the repeated stress concentration due to rolling of the tire increases the risk of fatigue breakage of the cord 31, so that the durability of the tire bead portion cannot be substantially improved. There was a problem.
[0004]
The present invention has an object to solve such problems of the proposed technique, and the object of the 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. or from the inside to the outside, which comprises at least one carcass ply wound around toward the outside to the inside, of the carcass cord of the winding-out turning portion, the carcass ply against the bead cores facing surface bead base side Of the extending portion on the surface of the bead core adjacent to the winding direction of the wire, and the acute angle α with respect to the central axis of the bead core, and the extending portion on the surface of the bead core further adjacent to the bead core surface in the winding direction of the carcass ply. , The acute angle β with respect to the bead core central axis ,
70 ° ≦ α <90 °
More preferably, 70 ° ≦ α <80 °
When α> β, α−β ≦ 20 °
More preferably, α−β ≦ 15 °
When α ≦ β, β−α ≦ 10 °
More preferably, the condition of β−α ≦ 8 ° is satisfied, and each of the extended portions of the carcass cord of the winding portion is connected to the carcass ply of the carcass cord at the winding end side of the carcass cord. It is close to the main body .
[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 of the carcass ply, the carcass ply is wound around the bead core and the carcass ply is wound around the bead core surface facing the bead base. The inclination angle α of the extending portion on the bead core surface adjacent to the direction is set to 70 ° or more and less than 90 °, and the bead core surface is further adjacent to the bead core surface in the winding direction of the carcass ply. The difference between the inclination angle β of the extended portion and the inclination angle α should be 20 ° or less or 10 ° or less. To ensure a long cord path around the bead core and sufficiently enhance the resistance of the carcass cord to pull out, the carcass cord suddenly changes under a relatively small angle change in the extending direction of the carcass cord. The extension direction of the carcass cord at the end of the carcass ply can be made sufficiently close to that of the carcass ply main body without damaging the durability of the bead as described above due to the angle change. Further, deformation or displacement in the circumferential direction at the winding portion of the carcass cord can be suppressed to reduce distortion at the ply end, and local stress concentration on the carcass cord can be prevented.
[0007]
Also, here, by setting the inclination angle α in the range of 70 ° or more and less than 90 °, deformation or displacement in the circumferential direction of the winding portion of the carcass cord in the radial tire is suppressed, and distortion at the end of the carcass ply is reduced. Can be made.
In other words, if it is less than 70 °, 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.
[0008]
Furthermore, if α> β,
α-β ≦ 20 °
This ensures a sufficiently long cord path around the bead core and sufficiently removes the possibility of pulling out the carcass cord. When the angle difference exceeds 20 °, winding forming becomes difficult.
[0009]
If α ≦ β,
β-α ≦ 10 °
This ensures a sufficiently long code path around the bead core. If the difference exceeds 10 °, the cord path becomes too short, and there is a high risk of pulling out the carcass cord, and winding forming becomes difficult.
[0010]
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.
[0011]
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 is enhanced.
[0012]
In addition, when the 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 advantageously prevent unexpected loosening of the winding portion. be able to.
[0013]
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.
[0014]
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.
[0015]
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.
[0016]
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. This is particularly advantageous.
[0017]
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.
[0018]
In this tire, as shown in FIG. 3, the winding portion 7 provided on the side portion 6 faces the bead base 3 a side of the ring-shaped bead core 4 of the carcass cord 10 constituting the carcass ply 5. The inclination angle of the extended portion 10a on the bead core surface 4b adjacent to the surface 4a in the winding direction of the carcass ply side portion 6 with respect to the bead core axis C, that is, FIG. The inclination angle α in the bead core surface development shown in FIG. 3 is 70 ° or more and less than 90 °, more preferably 70 ° or more and less than 80 °, and is further adjacent to the bead core surface 4b in the winding direction of the carcass ply 5. As shown in FIG. 3B, the inclination angle β of the extending portion 10b on the bead core surface 4c with respect to the bead core axis C is related to the inclination angle α.
When α> β, α−β ≦ 20 °
More preferably, α−β ≦ 15 °
On the other hand, as shown in FIG.
When α ≦ β, β−α ≦ 10 °
More preferably, β-α ≦ 8 °
And
[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 of the carcass ply is set to the carcass ply. The main body portion can be aligned with that of the main body portion, so that the displacement or deformation of the winding portion 7 in the circumferential direction due to the action of the tension on the carcass cord 10 is sufficiently suppressed, and the carcass cord tension is sufficiently uniform. It is possible to effectively improve the durability of the bead portion 3 by dispersing in the bead.
[0020]
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.
[0021]
【Example】
In the following, the bead portion durability test and the carcass cord pull-out resistance test of each of the example tire, the conventional tire, and the comparative tire will be described.
Here, the bead portion durability is in the heavy load radial tire of size 315/60 R22.5, and the tires 1 to 4 having the bead portion structure shown in FIGS. 1 and 3 and the winding structure shown in FIG. 5 and a conventional tire having a bead portion structure shown in FIG. 5, when a 9.00 × 22.5 rim is assembled and the filling air pressure is 900 kPa, the maximum load capacity is doubled. In a drum running test with a load equivalent to the above, it is obtained by measuring the running distance until it becomes impossible to run due to failure of the bead part (separation at the end of the carcass ply or the wire chafer end, etc.), and the conventional tire is used as a control The index was evaluated.
[0022]
The pull-out resistance of the carcass cord was evaluated by measuring the pressure until it was pulled out by applying water pressure inside.
[0023]
The results are shown in Table 1.
It should be noted that the larger the index value, the better the result.
[Table 1]

[0024]
According to Table 1, all of the example tires can greatly improve the bead durability as compared with the conventional tire and the comparative tire, and the pull-out resistance of the cord can be sufficiently increased. I understand that.
[0025]
【The invention's effect】
Thus, according to the present invention, in particular, the extended portion of the carcass cord of the winding portion on the bead core surface adjacent to the bead core surface facing the bead base side in the winding direction of the carcass ply is relative to the bead core central axis. The inclination angle is set to 70 ° or more and less than 90 °, and the difference between the same inclination angle of the extended portion on the surface of the bead core further adjacent to the surface in the winding direction of the carcass ply and the above inclination angle By specifying the value within a certain range, it is possible to sufficiently secure the pullout resistance of the carcass cord and greatly improve the durability of the tire bead portion.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an essential 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. 3A, showing a carcass cord extension mode 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, 10b Extension part (alpha), β Inclination angle C Bead core center axis b1, b2, b3 Bending part

Claims (6)

It extends toroidally between ring-shaped bead cores arranged in the bead part, and each side part is surrounded from the inner side in the tire width direction to the outer side or the outer side around the bead core whose cross-sectional shape is a polygon. In a pneumatic tire comprising at least one carcass ply wound inward from
Of the carcass cord of the winding-out turning portion, the extending portions with respect to the bead core surface facing the bead base side on a bead core surface adjacent to the wrapping direction of the carcass ply, an acute angle α with respect to the bead core center axis, to the bead core surface On the other hand, an acute angle β with respect to the bead core central axis of the extending portion on the bead core surface further adjacent to the winding direction of the carcass ply,
70 ° ≦ α <90 °
When α> β, α−β ≦ 20 °
When α ≦ β, β−α ≦ 10 °
Meet the conditions,
A pneumatic tire in which each of the extending portions of the carcass cord of the winding portion is brought close to the carcass ply main body portion of the carcass cord on the winding end side of the carcass cord . Tilt angle α
70 ≦ α <80
The pneumatic tire according to claim 1. Respective inclination angles α and β
When α> β, α−β ≦ 15
When α ≦ β, β−α ≦ 8
The pneumatic tire according to claim 1 or 2.   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 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, wherein a bead filler is disposed from an outer peripheral side of the winding portion of the carcass ply to a sidewall portion.

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