JP4276470B2 - Pneumatic tire - Google Patents

Description

【００３９】
表の如く、実施例のタイヤは、乗り心地性、リム組性、及びビード耐久性の維持を図りながら操縦安定性を向上しうるのが確認できる。
【００４０】
【発明の効果】
本発明は叙上の如く構成しているため、優れた乗り心地性やリム組性を確保でき、かつビード耐久性の低下を招くことなく操縦安定性を向上しうる。
【図面の簡単な説明】
【図１】本発明の空気入りタイヤの一実施例を示す断面図である。
【図２】そのビード部を拡大して示す断面図である。
【図３】従来技術を説明するタイヤの断面図である。
【符号の説明】
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 プライ本体部
６ｂ プライ折返し部
８ ビードエーペックスゴム
８Ａ エーペックス本体部
８Ｂ 翼部
９ ビード補強層
９Ａ 補強プライ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire with improved handling stability while maintaining bead durability.
[0002]
[Prior art]
Conventionally, for example, as shown in FIG. 3, a bead reinforcing layer a in which reinforcing cords are arranged at a predetermined angle is formed along the ply turn-up portion b1 of the carcass b, thereby suppressing the increase in the longitudinal rigidity of the tire. It has been practiced to improve steering stability while increasing directional rigidity and maintaining riding comfort and the like (see, for example, Patent Document 1).
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 6-72104
However, there is a limit to the improvement in steering stability by such a bead reinforcing layer a, and the height of the bead apex rubber c is increased in order to satisfy the demand for improvement in higher steering stability in recent years. Is desired.
[0005]
[Problems to be solved by the invention]
However, when the height of the bead apex rubber c is increased, the outer end portion of the bead apex rubber c approaches the outer end portion of the bead reinforcing layer a. However, there is a problem that the bead durability is lowered, for example, the carcass cord is broken or the bead reinforcing layer a is peeled off. In order to reduce the rigidity difference, when the bead apex rubber c is formed higher than the outer end portion of the bead reinforcement layer a, the bend durability is suppressed, but the bending rigidity of the sidewall portion is suppressed. Therefore, it is difficult to ensure excellent ride comfort and results in a loss of rim assembly.
[0006]
Therefore, the present invention forms a bead apex rubber with an apex main body having a triangular cross section and a thin plate-like wing extending from the outer end thereof, and the height of the apex main body from the bead base line, the height of the wing, And a pneumatic tire capable of improving driving stability without degrading bead durability, while ensuring excellent ride comfort and rim assembly, based on optimizing the height of the bead reinforcement layer and the like The purpose is to provide.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1 of the present application is folded around the bead core from the inner side to the outer side in the tire axial direction by a ply main body part extending from the tread part through the sidewall part to the bead core of the bead part. A carcass including at least one carcass ply provided with a series of ply folding portions, a bead apex rubber extending radially outward from the bead core between the ply body portion and the ply folding portion, and the bead apex rubber. With a bead reinforcement layer extending radially in the tire axial direction outside,
The bead reinforcing layer is made of a reinforcing ply in which reinforcing cords are arranged at 10 to 60 degrees with respect to the tire circumferential direction, and the height Ha from the bead base line is set to the flange height Hf of the rim from the bead base line. And 2.5 to 3.0 times the
The bead apex rubber includes an apex main body having a triangular cross section extending radially outward from the bead core to a point P having a height Hp 1.8 to 3.0 times the flange height Hf, and the apex main body. Consisting of a thin plate-like wing extending radially outward from the section,
And the thickness t of this wing is 1.0 to 2.0 times the diameter D of the carcass cord of the carcass ply,
Moreover, the total height Hb of the bead apex rubber from the bead base line is 3.5 times or more of the flange height Hf.
[0008]
In the invention of claim 1, the bead reinforcing layer extends radially outward from the radially outer surface of the bead core starting from the radially inner side along the outer surface of the ply folded portion. The height Hc from the bead base line is greater than the total height Hb of the bead apex rubber.
[0009]
In the invention of claim 2, the difference | Hp−Ha | between the height Hp of the point P and the height Ha of the bead reinforcing layer is 0.7 times or less of the flange height Hf. It is a feature.
[0010]
Furthermore, the invention of claim 3 is characterized in that the reinforcing cord of the bead reinforcing layer is an organic fiber cord.
[0011]
The invention according to claim 4 is characterized in that a flatness ratio, which is a ratio W / T of a tire cross-section height T and a tire cross-section width W, is 75% or less, and the rim is a 5 ° taper rim.
[0012]
In the present specification, various dimensions of the tire including the heights Ha, Hb, Hc, and Hp are values in a normal internal pressure state in which a normal rim is assembled and filled with a normal internal pressure unless otherwise specified.
[0013]
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, “Design Rim” for TRA, or ETRTO means "Measuring Rim". The “regular internal pressure” is the air pressure specified by the tire for each tire. The maximum air pressure in the case of JATMA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the case of TRA, If it is ETRTO, it is "INFLATION PRESSURE", but if it is a tire for passenger cars, it will be 180 KPa.
The “bead base line” means a tire axial line passing through a rim diameter position defined by the standard.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a normal internal pressure state of the pneumatic tire of the present invention, and FIG. 2 is an enlarged cross-sectional view showing a bead portion thereof.
[0016]
In FIG. 1, a pneumatic tire 1 includes a carcass 6 extending from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, and a belt disposed inside the tread portion 2 and outside the carcass 6. With layer 7.
[0017]
The belt layer 7 is composed of two or more belt plies 7A and 7B in this example in which highly elastic belt cords are arranged at an angle of, for example, 10 to 70 ° with respect to the tire circumferential direction. Each belt ply 7A, 7B enhances belt rigidity by crossing the belt cords between the plies, and reinforces substantially the entire width of the tread portion 2 with a tagging effect. As the belt cord, a steel cord or a high modulus organic fiber cord such as an aromatic polyamide fiber comparable to the steel cord can be preferably used.
[0018]
Further, on the outer side of the belt layer 7, a band layer 10 in which an organic fiber cord such as nylon is spirally wound, for example, at an angle of 5 degrees or less with respect to the tire circumferential direction is formed, and lifting of the tread portion 2 accompanying high speed running is performed. It is desirable to prevent.
[0019]
The carcass 6 is composed of one or more carcass plies 6A in which carcass cords are arranged at an angle of, for example, 75 to 90 ° with respect to the tire circumferential direction, and in this example, one carcass ply 6A. Organic fiber cords such as are preferably used.
[0020]
The carcass ply 6A includes a series of ply folding portions 6b that are folded from the inner side to the outer side in the tire axial direction around the bead core 5 at both ends of the ply main body portion 6a straddling the bead cores 5 and 5.
[0021]
The bead portion 4 includes a bead apex rubber 8 extending between the ply main body portion 6a and the ply turn-up portion 6b and extending radially outward from the bead core, and an outer side of the bead apex rubber 8 in the tire axial direction. And a bead reinforcing layer 9 extending in the radial direction.
[0022]
The bead reinforcing layer 9 is formed of one or two reinforcing plies 9A in this example, in which reinforcing cords made of organic fiber cords such as nylon are arranged at 10 to 60 degrees with respect to the tire circumferential direction. . Further, as shown in an enlarged view in FIG. 2, the bead reinforcement layer 9 is radially outward along the outer surface of the ply turn-up portion 6b with the radially inner side as a starting point Q rather than the radially outer surface of the bead core 5. Extend.
[0023]
Such a bead reinforcement layer 9 has organic fiber reinforcement cords arranged in the above-mentioned angular range, so that it can increase the circumferential rigidity while suppressing an increase in the longitudinal rigidity of the tire, ensuring excellent ride comfort In addition, the steering stability can be improved. If the angle of the reinforcing cord exceeds 60 degrees, the increase in longitudinal rigidity becomes remarkable, resulting in a decrease in ride comfort. Conversely, if the angle is less than 10 degrees, it is difficult to manufacture a tire. Therefore, the array angle is more preferably in the range of 15 to 55 degrees.
[0024]
Further, in the bead reinforcement layer 9, the radial height Ha from the bead base line BL needs to be 2.5 to 3.0 times the flange height Hf of the rim R from the bead base line BL. is there. When the height Ha is less than 2.5 times the flange height Hf, the reinforcing range is too small to expect improvement in steering stability. On the contrary, when the height Ha is more than 3.0 times, the reinforcing cord has the above angle. Even in the range, the result is that the longitudinal rigidity is increased and the ride comfort is lowered.
[0025]
In the pneumatic tire 1, the bead apex rubber 8 is configured as follows in order to maintain excellent ride comfort by the bead reinforcing layer 9 and to further improve the handling stability without impairing the bead durability. ing.
[0026]
That is, the bead apex rubber 8 has a substantially constant thickness t from the apex main body portion 8A having a triangular cross section extending radially outward from the bead core 5 and the point P which is the outer end thereof. And a thin wing portion 8B extending outward in the radial direction. In addition, “substantially constant thickness” means that thickness variation due to vulcanization pressure or the like at the time of tire molding and taper at the tip can be allowed.
[0027]
In this bead apex rubber 8, the height Hp of the point P from the bead base line BL, that is, the height Hp of the apex body 8A is 1.8 to 3.0 times the flange height Hf, and The total height Hb of the entire bead apex rubber 8 from the bead base line BL is set to be 3.5 times or more of the flange height Hf, and the thickness t of the wing portion 8B is set to 1. of the diameter D of the carcass cord. The range is 0 to 2.0 times.
[0028]
Thus, since the height Hp of the apex body 8A having a large rubber volume is increased to 1.8 × Hf to 3.0 × Hf, the steering stability can be further improved. Further, since the wing portion 8B is extended from the outer end P of the apex main body portion 8A, the occurrence of a rigidity step due to the outer end P approaching the outer end of the bead reinforcing layer 9, that is, the occurrence of local bending deformation. It is possible to suppress a decrease in bead durability, such as preventing the carcass cord from being broken and peeling at the outer end of the bead reinforcing layer 9. Further, since the thickness t of the wing portion 8B is as thin as 1.0 × D to 2.0 × D, the bending rigidity does not increase, so that excellent riding comfort and rim assembly can be maintained. It becomes possible.
[0029]
Here, if the height Hp is less than 1.8 × Hf, further improvement in steering stability cannot be expected. On the other hand, when the height Hp is greater than 3.0 × Hf and the thickness t is greater than 2.0 × D, the rigidity tends to increase, leading to a decrease in ride comfort and rim assembly. On the other hand, if the thickness t is less than 1.0 × D and the total height Hb is less than 3.5 × Hf, the rigidity step is not sufficiently relaxed, and the decrease in bead durability cannot be suppressed.
[0030]
In this example, the difference | Hp−Ha | between the height Hp of the apex body 8A and the height Ha of the bead reinforcement layer 9 is 0.7 times or less of the flange height Hf. However, even in such a case, a decrease in bead durability can be suppressed. The bead apex rubber 8 is made of hard rubber having a rubber hardness (durometer A hardness) of 75 to 95 °, and the apex body 8A and the wing 8B are formed of the same material.
[0031]
The ply turn-up portion 6b of the carcass 6 has a height hb from the bead base line BL larger than the total height Hb of the bead apex rubber 8, and after the outer end of the bead apex rubber 8 is exceeded, It extends along the ply body 6a.
[0032]
In the present invention, the flatness, which is the ratio W / T of the tire cross-section height T and the tire cross-section width W, is 75% or less, and is mounted on a 5 ° taper rim, for example, for passenger cars, light trucks, and compact. It can be suitably used for truck tires, particularly small truck tires used under high load loads.
[0033]
As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.
[0034]
【Example】
A tire having the structure shown in FIG. 1 and having a tire size of 205 / 70R15 was manufactured based on the specifications shown in Table 1, and the test stability, ride comfort, bead durability, and rim assembly of each sample tire were tested and compared. . The specifications other than those shown in Table 1 were the same.
[0035]
(1) Steering stability and ride comfort;
Steering tires mounted on four wheels of a vehicle (1 Box) with a rim (5.5K x 15) and internal pressure (350 kPa), and driving stability when riding on a tire test course on a dry asphalt road surface (feeling of rigidity and steering wheel) Responsiveness) and ride comfort were evaluated by a 10-point method with 6 points in the conventional example by sensory evaluation of the driver. A larger value is better.
[0036]
(2) Bead durability;
A sample tire was tested under the conditions of rim (5.5K × 15), internal pressure (maximum air pressure specified by JATMA; 600 kPa), load (200% of JATMA's maximum load load; 18.63 kPa), and speed (20 km / h). Then, the drum was run for 400 hours, and then the tire was disassembled to investigate the presence or absence of peeling damage.
[0037]
(3) Rim assembly;
The sample tires were assembled by rim assembly by hand using only levers on a JATMA standard rim, and evaluated by a 10-point method with 6 conventional examples according to the sensuality of the operator. A larger value is better.
[0038]
[Table 1]

[0039]
As shown in the table, it can be confirmed that the tires of the examples can improve steering stability while maintaining ride comfort, rim assembly, and bead durability.
[0040]
【The invention's effect】
Since the present invention is configured as described above, it is possible to ensure excellent ride comfort and rim assembly, and to improve steering stability without causing a decrease in bead durability.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of a pneumatic tire according to the present invention.
FIG. 2 is an enlarged cross-sectional view of the bead portion.
FIG. 3 is a cross-sectional view of a tire for explaining the prior art.
[Explanation of symbols]
2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 6A Carcass ply 6a Ply main part 6b Ply turn part 8 Bead apex rubber 8A Apex main part 8B Wing part 9 Bead reinforcement layer 9A Reinforcement ply

Claims (4)

The ply body part extending from the tread part through the sidewall part to the bead core of the bead part includes at least one carcass ply provided with a series of ply turn-up parts that turn the bead core around from the inner side to the outer side in the tire axial direction. A carcass, a bead apex rubber extending radially outward from the bead core between the ply body part and the ply folded part, and a bead reinforcement layer extending radially in the tire axial direction of the bead apex rubber;
The bead reinforcing layer is made of a reinforcing ply in which reinforcing cords are arranged at 10 to 60 degrees with respect to the tire circumferential direction, and the height Ha from the bead base line is set to the flange height Hf of the rim from the bead base line. And 2.5 to 3.0 times the
The bead apex rubber includes an apex main body having a triangular cross section extending radially outward from the bead core to a point P having a height Hp 1.8 to 3.0 times the flange height Hf, and the apex main body. Consisting of a thin plate-like wing extending radially outward from the section,
And the thickness t of this wing is 1.0 to 2.0 times the diameter D of the carcass cord of the carcass ply,
Moreover, the total height Hb of the bead apex rubber from the bead base line is not less than 3.5 times the flange height Hf ,
Further, the bead reinforcing layer extends radially outward from the radially outer surface of the bead core along the outer side surface of the ply folded portion as a starting point, and extends from the bead base line of the ply folded portion. A pneumatic tire characterized in that the height Hc is greater than the total height Hb of the bead apex rubber .   The difference | Hp-Ha | between the height Hp of the point P and the height Ha of the bead reinforcement layer is 0.7 times or less of the flange height Hf. Pneumatic tire. The pneumatic tire according to claim 1 or 2 , wherein the reinforcement cord of the bead reinforcement layer is an organic fiber cord. Flatness ratio is the ratio W / T of the tire section height T and the tire section width W is 75% or less, and according to any one of claims 1 to 3, wherein the rim is 5 ° Teparimu Pneumatic tire.

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