JP2005008069A - Radial-ply pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radial ply pneumatic tire equipped with an enhanced durability while it can exert an excellent vibration performance and noise performance. <P>SOLUTION: The radial-ply pneumatic tire includes carcass cords 10 each formed as a two-component twined cord consisting of the first 10A and the second strand 10B made from polyethylene 2, 6 naphthalate fibers. The sub-twining number n1 of the first strand 10A is 15-40 pcs/10 cm, while the sub-twining direction of the second strand 10B should be the same as that of the first 10A and the sub-twining number n2 be 1.1-1.5 times as large as n1. The over-twinings are made in the opposite direction to the sub-twining direction where the over-twining number n3 should be larger than n1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００２７】
表の如く実施例のタイヤは、優れたロードノイズ性能を発揮しながら高速耐久性が向上しているのが確認できる。
【００２８】
【発明の効果】
叙上のごとく本発明は、下撚り数を違えた２本のストランドを、所定の上撚り数で撚り合わせたＰＥＮコ一ドをカーカスコードに採用しているため、優れた振動・騒音性能を発揮しながらタイヤ耐久性を向上することができる。
【図面の簡単な説明】
【図１】発明の一実施例の空気入りラジアルタイヤを示すタイヤの断面図である。
【図２】カーカスコードを誇張して示す線図である。
【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
６Ａ カーカスプライ
１０ カーカスコード
１０Ａ、１０Ｂ 第１、第２のストランド[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic radial tire that has improved durability while exhibiting excellent vibration and noise performance by using a polyethylene terephthalate cord having an improved twisted structure as a carcass cord.
[0002]
[Prior art]
Conventionally, as a carcass cord for a pneumatic radial tire, a fiber such as nylon, rayon, or polyester is generally used in a passenger car. Particularly, polyester such as polyethylene terephthalate (PET) improves tire rigidity and uniformity. The current carcass cord has become the mainstream for reasons such as improving flat spots.
[0003]
However, with the recent improvement of the road network and the high performance of vehicles, the performance required for tires has become increasingly severe, and the generation of vibration and noise has become a major problem. Therefore, in recent years, it has been proposed to employ polyethylene 2, 6 naphthalate (PEN), which has a higher elastic modulus among the same polyesters, as the carcass cord (see, for example, Patent Documents 1 to 3).
[0004]
[Patent Document 1]
JP-A-7-309102 [Patent Document 1]
2000-185508 [Patent Document 1]
No. 2000-177310 gazette
[Problems to be solved by the invention]
However, although the PEN code has a great effect in reducing vibration and noise, it has a higher elastic modulus than PET and is inferior in fatigue resistance. It is necessary to improve the durability of the tire.
[0006]
Therefore, the present invention is based on the principle that two strands having different numbers of lower twists are twisted together with a predetermined number of upper twists in the PEN cord, while exhibiting excellent vibration and noise performance and improving tire durability. An object of the present invention is to provide a pneumatic radial tire that can be improved.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1 of the present application is a pneumatic radial tire having a carcass ply extending from a tread portion through a sidewall portion to a bead core of a bead portion,
The carcass cord arranged in the carcass ply has a double twist structure in which first and second strands made of polyethylene 2, 6 naphthalate fiber and twisted together are twisted together by an upper twist,
The first twist of the first strand is 15 to 40 times / 10 cm of the number of lower twists / 10 cm,
In the second strand, the lower twist is the same direction as the first twist of the first strand, and the lower twist number n2 is 1.1 to 1.5 times the lower twist number n1,
In addition, in the first twist of the first and second strands, the upper twist direction is opposite to the first twist direction of the first and second strands, and the upper twist number n3 is larger than the lower twist number n1. It is characterized by.
[0008]
According to a second aspect of the present invention, the upper twist number n3 is 1.0 to 2.0 times the lower twist number n2.
[0009]
In the invention of claim 3, the first and second strands are characterized in that the number of the polyethylene 2 and 6 naphthalate fibers is in the range of 150 to 350, respectively.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a meridional cross-sectional view when the pneumatic radial tire of the present invention is a passenger tire.
In FIG. 1, a pneumatic radial tire 1 (hereinafter referred to as a tire 1) includes a carcass 6 that extends from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, an inner side of the tread portion 2, and the carcass 6. And at least a belt layer 7 disposed outside.
[0011]
The carcass 6 is formed of one or more, in this example, one carcass ply 6A in which carcass cords are arranged at an angle of 75 to 90 ° with respect to the tire circumferential direction. The carcass ply 6 </ b> A includes ply folding portions 6 b that are folded from the inner side to the outer side in the tire axial direction around the bead core 5 on both sides of the ply main body portion 6 a that extends between the bead cores 5 and 5. A bead apex rubber 8 is provided between the ply body portion 6a and the ply turn-up portion 6b so as to taper outward from the bead core 5 in the radial direction.
[0012]
In the present invention, as the carcass cord 10, as conceptually shown in FIG. 2, first and second strands 10 </ b> A and 10 </ b> B made of polyethylene 2 and 6 naphthalate (PEN) fibers and twisted, It is formed by a cord having a double twist structure that is twisted together by twisting.
[0013]
At this time, the first strand 10 </ b> A has a lower twist n1 of 15 to 40 times / 10 cm, and the second strand 10 </ b> B has a lower twist in the direction of the first strand 10 </ b> A. In the same direction as the twisting direction, the number of twists n2 is 1.1 to 1.5 times the number of twists n1. In addition, the first twist of the first and second strands 10A and 10B is twisted in the direction opposite to the twisting direction of the first and second strands 10A and 10B and the number of twists n3 is the lower twist. It is larger than the number n1.
[0014]
As described above, the untwisted twist structure is made such that the first and second strands 10A and 10B have different numbers of primary twists n1 and n2, and the primary twist number n3 is larger than the primary twist number n1. As a result, while improving fatigue resistance with a high number of twists n2 and n3, a decrease in cord strength and elastic modulus can be kept low with a low number of twists n1, and tires exhibiting excellent vibration and noise performance Durability can be improved.
[0015]
Here, when the number of lower twists n1 is less than 15 times / 10 cm and the number of lower twists n2 is less than 1.1 times the number of lower twists n1, the effect of improving fatigue resistance is not exhibited, and conversely the number of lower twists When n1 is larger than 40 times / 10 cm and larger than 1.5 times the number of primary twists n1, the strength and elastic modulus of the cord are remarkably lowered, and in any case, fatigue resistance, strength and elastic modulus It becomes difficult to achieve both. Further, even if the number of upper twists n3 is equal to or less than the number of lower twists n1, the effect of improving the fatigue resistance is not exhibited. Therefore, the number of upper twists n3 is preferably 1.0 times or more, more preferably 1.1 times or more of the number of lower twists n2, from the viewpoint of fatigue resistance. If the number of upper twists n3 exceeds 2.0 times the number of lower twists n2, the strength and elastic modulus of the cord will be excessively reduced. Therefore, the number of upper twists n3 is not more than 2.0 times the number of lower twists n2, Is preferably 1.6 times or less.
[0016]
When PEN fibers are used for the carcass cord 10, the cord thickness is preferably 500 to 3000 dtex. If the cord thickness is less than 500 dtex, the number of plies is increased in order to ensure the carcass strength necessary for the tire. On the other hand, if it exceeds 3000 dtex, the cord becomes thick and the ply thickness increases.
[0017]
Further, in the first and second strands 10A and 10B, the number of PEN fibers is preferably in the range of 150 to 350, and if it exceeds 350, the fibers are too thin, There is a tendency that the strength of the cord is reduced by rubbing. On the other hand, if the number is less than 150, the riding comfort of the tire tends to be impaired, for example, the fiber is too thick and the bending rigidity of the cord increases. From such a viewpoint, the number of PEN fibers in each of the strands 10A and 10B is more preferably in the range of 150 to 250.
The number of the first strands 10A is in the range of 240 to 350, the number of the second strands is in the range of 150 to 260, and the number of the first strands 10A is increased to maintain durability. It is preferable in that it is more effective for improvement.
[0018]
Then, the carcass ply 6A is formed by arranging the carcass cords of such PEN fibers at a cord driving number of 30 to 60 pieces / 5 cm. The PEN fiber may be not only a homopolymer but also a copolymer composed of 85 mol% or more of polyethylene 2,6 naphthalate and less than 15 mol% of a copolymerizable third component. Examples of the third component include naphthalene dicarboxylic acid other than 2,6 naphthalene dicarboxylic acid, terephthalic acid, isophthalic acid, diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, and the like.
[0019]
Next, as shown in FIG. 1, the belt layer 7 has two or more, or two, in this example, two high-strength belt cords such as steel cords arranged at an angle of 15 ° to 40 ° with respect to the tire circumferential direction. It is formed from belt plies 7A and 7B. 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.
[0020]
In this example, a band ply in which band cords of organic fibers are arranged at an angle of 5 degrees or less with respect to the circumferential direction on the outer side in the radial direction of the belt layer 7 for the purpose of improving high-speed durability and steering stability. The case where the band layer 9 which consists of 9A is provided is illustrated. As the band ply 9A, a pair of left and right edge band plies that covers only the outer end portion of the belt layer 7 or a full band ply that covers substantially the entire width of the belt layer 7 can be used. 9 is formed. In this example, the case where the band layer 9 consists of one full band ply is illustrated. Nylon, polyester, rayon, aromatic polyamide, etc. can be used as the band cord. In particular, the cord of the PEN fiber according to the present invention, that is, the untwisting and the upper twisting are regulated in the same manner as in the case of the carcass cord 10. It is preferable to use a balanced twisted cord from the viewpoint of handling stability.
[0021]
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.
[0022]
【Example】
A tire having a tire size of 195 / 65R15 having the structure shown in FIG. 1 was prototyped based on the specifications shown in Table 1, and the high speed durability, road noise, and residual strength of the carcass cord of each sample tire were measured and compared.
The specifications of the carcass, belt layer, and band layer other than those in Table 1 are the same as follows.
・ Number of carcass plies: 1
Cord angle: 90 degrees,
Number of cords driven: 50 / 5cm,
・ Number of belt layer plies: 2
Code: Steel, 1x3x0.23HT,
Cord angle: +20 degrees / -20 degrees
Number of cords driven: 40 / 5cm,
・ Number of band layer plies: 1 (full band ply),
Code: 1400 dtex / 2 (nylon 66),
Number of cords driven: 49 / 5cm, 10mm wide strip ply spiral winding
(1) High speed durability;
Using a drum running tester, starting from 80 km / h at an internal pressure (250 kPa) and load (2.45 kN), increasing the speed by 10 km / h every 10 minutes running until running The distance was expressed as an index with Comparative Example 1 as 100. The larger the value, the better.
[0024]
(2) Road noise;
It was mounted on all wheels of a passenger car (2000 cc) at an internal pressure (200 kPa), traveled on a smooth road surface at a speed of 60 km / h, and a sound pressure of 250 Hz and 315 Hz was measured at the position of the backrest of the driver's seat. The reciprocal of the value was displayed as an index with Comparative Example 1 as 100. The larger the value, the lower the road noise and the better.
[0025]
(3) Residual strength;
Using a drum tester, the vehicle was run for 10,000 m at a speed of 80 km / h under the conditions of the internal pressure specified in JIS and the maximum load specified in JIS, and the carcass cord was taken out after dismantling the tire after running. Then, the taken carcass cord was measured for the load g at break according to JIS L1017 (chemical fiber tire cord test method), Section 7.5 (tensile strength and elongation), before rubber drawing (after DIP treatment) ) In a ratio g / G to the load G when the carcass cord is broken. The larger the value, the higher the residual strength and the better the fatigue resistance.
[0026]
[Table 1]

[0027]
As shown in the table, it can be confirmed that the tires of the examples have improved high-speed durability while exhibiting excellent road noise performance.
[0028]
【The invention's effect】
As described above, the present invention employs a PEN cord in which two strands having different numbers of lower twists are twisted at a predetermined upper twist number in a carcass cord, so that excellent vibration and noise performance is achieved. The tire durability can be improved while exhibiting.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a tire showing a pneumatic radial tire according to an embodiment of the invention.
FIG. 2 is a diagram exaggeratingly showing a carcass cord.
[Explanation of symbols]
2 Tread portion 3 Side wall portion 4 Bead portion 5 Bead core 6A Carcass ply 10 Carcass cords 10A and 10B First and second strands

Claims (3)

A pneumatic radial tire having a carcass ply extending from a tread portion to a bead core of a bead portion through a sidewall portion,
The carcass cord arranged in the carcass ply has a double twist structure in which first and second strands made of polyethylene 2, 6 naphthalate fiber and twisted together are twisted together by an upper twist,
The first twist of the first strand is 15 to 40 times / 10 cm of the number of lower twists / 10 cm,
In the second strand, the lower twist is the same direction as the first twist of the first strand, and the lower twist number n2 is 1.1 to 1.5 times the lower twist number n1,
In addition, in the first twist of the first and second strands, the upper twist direction is opposite to the first twist direction of the first and second strands, and the upper twist number n3 is larger than the lower twist number n1. Pneumatic radial tire characterized by. The pneumatic radial tire according to claim 1, wherein the number of upper twists n3 is 1.0 to 2.0 times the number of lower twists n2. 3. The pneumatic radial tire according to claim 1, wherein the first and second strands have a number of the polyethylene 2 and 6 naphthalate fibers in the range of 150 to 350, respectively.

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