JP4268365B2 - Pneumatic radial tire - Google Patents

Description

【００３７】
実施例は、耐久性を維持或いは向上しながらロードノイズを大幅に低減しうるのが確認できる。
【００３８】
【発明の効果】
叙上のごとく本発明の空気入りタイヤは、バンドコードとして、コード太さ、撚り数、初期モジュラス及びこの初期モジュラスの２５℃〜７０℃の温度範囲における変化率等を特定したポリエチレン２，６ナフタレート繊維コードを用いているため、耐久性を確保しながらロードノイズ低減効果をより有効に発揮できる。
【図面の簡単な説明】
【図１】発明の一実施例を示すタイヤの断面図である。
【図２】帯状プライの構造を示す斜視図である。
【符号の説明】
２ トレッド部
６ カーカス
７ ベルト層
９ バンド層
１０ バンドコード
９Ａ バンドプライ
１４ ポリエチレン２，６ナフタレート繊維コード[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic radial tire with reduced road noise.
[0002]
[Background Art and Problems to be Solved by the Invention]
In general, in a pneumatic radial tire, in order to improve high-speed durability, a band layer made of a band ply in which a band cord is spirally wound is provided outside the belt layer.
[0003]
And, it has been found that providing such a band layer reduces road noise (in-vehicle noise) in the vicinity of a frequency of 250 Hz in addition to the improvement of the high-speed durability. Instead, using high modulus fiber cords such as aromatic polyamide fiber cords, polyethylene terephthalate fiber cords, polyethylene naphthalate fiber cords, etc., it has been found that the road noise reduction effect can be increased by increasing the binding force on the belt layer. I came.
[0004]
However, as a result of the inventor's research, it has been found that it is difficult to effectively exhibit the road noise reduction effect simply by increasing the modulus of the band code.
[0005]
This includes a step of pressing a raw tire against a vulcanization mold when the tire is vulcanized, and at this time, the tire is generally given a stretch of 1 to 3%. However, it has been found that if an extremely high modulus cord is used as the band cord, the band cord cannot be expanded during vulcanization molding, causing tire deformation, which hinders the effect of reducing road noise.
[0006]
Therefore, in order to reduce road noise, it is necessary to increase the modulus of the band cord in consideration of the tire deformation. In general, in a pneumatic tire, the tread temperature rises to near 70 ° C by running. In order to reduce the road noise, the variation of the modulus due to the temperature of the band cord is further changed to the temperature range up to 70 ° C. It was also found that it is important to suppress the band cord as much as possible, and to exert the restraint force by the band cord stably while driving.
[0007]
Therefore, the present invention basically uses a polyethylene 2,6 naphthalate fiber cord in which the cord thickness, the number of twists, the initial modulus, and the rate of change of the initial modulus in the temperature range of 25 ° C. to 70 ° C. are specified as the band cord. Therefore, it is an object of the present invention to provide a pneumatic radial tire that can more effectively exert a road noise reduction effect.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1 of the present application is a pneumatic comprising a belt layer disposed inside a tread portion and outside a carcass, and a band layer disposed outside the belt layer. A radial tire,
The band layer is made of a band ply the band cord is wound spirally at an angle of less than 5 degrees with respect to the tire circumferential direction, and the band cords, cord thickness is 2500～3600D, twisting number twisting While using a polyethylene 2,6 naphthalate fiber cord having a number of 30 to 35 times / 10 cm,
The polyethylene 2,6 naphthalate fiber cord is characterized in that the initial modulus at 25 ° C. is 50 to 65 gf / d and the change rate of the initial modulus between 25 ° C. and 70 ° C. is ± 20% or less.
[0009]
According to a second aspect of the present invention, the polyethylene 2,6 naphthalate fiber cord is characterized in that the elongation of the cord at a load of 2.0 gf / d is 0.5 to 2.5%.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a meridional section when the pneumatic radial tire of the present invention is a passenger tire.
[0011]
In FIG. 1, a pneumatic radial tire 1 is disposed on 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, inside the tread portion 2, and outside the carcass 6. A belt layer 7 and a band layer 9 disposed on the outer side of the belt layer 7 are provided.
[0012]
The carcass 6 is formed of one or more carcass plies 6A in this example, in which carcass cords are arranged at an angle of 70 to 90 ° with respect to the tire circumferential direction. The carcass ply 6A includes a folded portion 6b folded around the bead core 5 on both sides of the ply body portion 6a straddling the bead cores 5 and 5, and between the ply body portion 6a and the folded portion 6b, A bead apex rubber 8 for bead reinforcement extending in a radial manner from the bead core 5 to the outside in the radial direction is disposed.
[0013]
As a carcass cord, in the case of a tire for a passenger car, an organic fiber cord such as nylon, polyester, rayon, aromatic polyamide or the like is suitably employed, but a steel cord can also be employed depending on the tire size, category, or the like.
[0014]
Further, the belt layer 7 includes two or more belt plies 7A and 7B in which high strength belt cords such as steel cords are inclined and arranged at an angle of 10 ° to 35 ° with respect to the tire circumferential direction. It is formed. The belt plies 7A and 7B are stacked in different directions so that the belt cords cross each other between the plies, thereby increasing the belt rigidity and reinforcing the substantially full width of the tread portion 2 with a tagging effect. .
[0015]
The ply width of the radially inner belt ply 7A is wider than that of the outer belt ply 7B, and this ply width constitutes the belt width WB of the belt layer 7.
[0016]
Next, the band layer 9 is formed from one or more band plies 9A, in this example, one band ply 9A, in which the band cord 10 is spirally wound at an angle of 5 degrees or less with respect to the tire circumferential direction. In this example, the case where the band ply 9A is a so-called full band that covers substantially the entire width of the belt layer 7 is illustrated, but it is formed as a so-called edge band on both sides that covers only both ends of the belt layer 7. You can also. As for the full band, “covering substantially the entire width” of the belt layer 7 means covering 95% or more of the belt width WB, and in this example, the width W of the band ply is the belt width WB. The case where it is substantially equal is illustrated.
[0017]
Further, as shown in FIG. 2, the band ply 9A includes a tape-like band-like ply 13 formed by embedding one band cord 10 or an aligned body of a plurality of band cords 10 in a topping rubber 12. It is formed by spirally winding along the circumferential direction, and at this time, the angle formed by the band cord 10 and the tire circumferential direction is set to 5 degrees or less. The band ply 9 </ b> A formed by such a spiral winding has a so-called jointless structure with no seam, so that it has excellent tire uniformity and increases the restraining force on the belt layer 7 to improve its tagging effect. In this example, for example, a band ply 13 having a width W1 of about 10 mm, for example, in which about 10 band cords 10 are arranged and buried is illustrated.
[0018]
In the present embodiment, as the band cord 10, a polyethylene 2,6 naphthalate fiber cord 14 having a cord thickness of 2500-3600d and a twist number of 30-40 times / 10 cm is used, and the polyethylene 2,6 naphthalate fiber is used. The initial modulus M of the cord 14 at 25 ° C. is restricted to a range of 50 to 65 gf / d, and the rate of change of the initial modulus M between 25 ° C. and 70 ° C. is reduced to a range of ± 20% or less.
[0019]
The number of twists of 30 to 40 times / 10 cm means that both the number of lower twists and the number of upper twists are 30 to 40 times / 10 cm. In particular, the number of lower twists and the number of upper twists are the same. A twisted structure can be suitably employed. In the present invention, the number of twists is 30 to 35 times / 10 cm.
[0020]
The polyethylene 2,6 naphthalate fiber is 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. good. 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.
[0021]
As described above, the band cord 10 is made of polyethylene 2,6 naphthalate fiber to increase the modulus, the initial modulus M is increased to a range of 50 to 65 gf / d, and the temperature range in the tread portion 2 during use of the tire. By suppressing the tension change of the band cord 10 in the belt, the effect of the belt layer 7 can be made uniform and the circumferential rigidity of the tread portion 2 becomes large and uniform, so that it is difficult to pick up vibrations on the road surface when the tire is running. Thus, road noise is reduced.
[0022]
Here, first, the strength and elongation of the band cord 10, in order to obtain a proper balance between the fatigue resistance, Ru important that the number of twists of cord 30 to 40 times / 10 cm. In particular, in the present invention, the number of twists is 30 to 35 times / 10 cm. If it is less than 30 times / 10 cm, the elongation and fatigue resistance become insufficient, and the required durability cannot be obtained. If the number of twists exceeds 40 times / 10 cm, the elongation of the cord becomes excessive, and even when polyethylene 2,6 naphthalate fiber is used, the initial modulus M in the above range cannot be obtained.
[0023]
In general, examples of high modulus fibers include aromatic polyamide fibers and polyethylene terephthalate fibers. For example, when aromatic polyamide fibers are used, the modulus is too high as described above, and the vulcanization moldability is impaired. Tire deformation occurs during vulcanization molding, and road noise reduction effect cannot be fully exhibited. In addition, the aromatic polyamide fiber has a large energy loss (tan δ) as compared with the polyethylene 2,6 naphthalate fiber of this embodiment, and is therefore disadvantageous for the rolling resistance performance. Polyethylene terephthalate fibers have insufficient modulus and are excellent in vulcanization moldability, but it is difficult to increase the initial modulus M to the above range, and the effect of reducing road noise cannot be sufficiently exhibited.
[0024]
On the other hand, in the polyethylene 2,6 naphthalate fiber, it is possible to secure an initial modulus M of 50 to 65 gf / d while setting the number of twists to 30 to 35 times / 10 cm. It is possible to effectively exhibit the road noise reduction effect while keeping the balance of the vehicle properly. At this time, the thickness of the polyethylene 2,6 naphthalate fiber cord 14 is in the range of 2500 to 3600d, the cord strength is insufficient if it is less than 2500d, and the band ply 9A becomes thicker than necessary if it exceeds 3600d. Disadvantageous.
[0025]
Here, the band cord 10 in the tire is embedded with an elongation of about 1 to 3% by stretching at the time of vulcanization molding. When considering the sulfur formability, the modulus at the low elongation, that is, the initial modulus M is important. If the initial modulus M is less than 50 gf / d, the restraining force on the belt layer 7 is too small, and if it exceeds 65 gf / d, the vulcanization moldability is impaired and the tire tends to deform. Even in this case, the road noise reduction effect cannot be fully exhibited.
[0026]
The initial modulus M means the inclination at the origin of the “load-elongation” curve of the cord determined in accordance with the chemical fiber tire cord test method of JIS L1017.
[0027]
In the polyethylene 2,6 naphthalate fiber cord 14, it is also important to regulate the rate of change of the initial modulus M between 25 ° C. and 70 ° C. to ± 20% or less. That is, assuming that the maximum value of the initial modulus in the temperature range of 25 ° C. to 70 ° C. is Mmax and the minimum value is Mmin, the differences Mmax-M and M-Mmin from the initial modulus M at 25 ° C. are It is important that the initial modulus M be 20% or less.
[0028]
In order to reduce road noise, it is necessary to keep the fluctuation of the initial modulus M low and to keep the band cord restraining force constant during running within the temperature range of the tread portion 2 during tire use. This is because if the rate of change exceeds ± 20%, the tension of the band cord 10 excessively fluctuates as the temperature rises during traveling, and the effect of reducing road noise is impaired. From such a viewpoint, the rate of change is preferably ± 15% or less, and more preferably ± 10% or less.
[0029]
The polyethylene 2,6-naphthalate fiber cord contains 90% or more of ethylene 2,6-naphthalate units, the DSC peak is 280 ° C. or more, the intrinsic viscosity is 0.7 or more, and the birefringence is 0.30 or more. By setting it as such, the change rate as described above is low and the thermal stability can be improved. In addition, there is a possibility that the rate of change can be controlled by the processing conditions during the RFL treatment, the number of twists of polyethylene 2,6 naphthalate fiber cord, the fineness, the number of filaments, and the like.
[0030]
In the band cord 10, from the viewpoint of dimensional stability of the tire, the elongation of the band cord 10 at a load of 2.0 gf / d is preferably in the range of 0.5 to 2.5%. It is expected that road noise will be generated due to the deterioration of the uniformity of the dimensional stability.
[0031]
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.
[0032]
【Example】
A tire having a structure shown in FIG. 1 and having a tire size of 195 / 65R15 was made on the basis of the specifications shown in Table 1, and the road noise and durability of each sample tire were tested. The results are shown in Table 1.
[0033]
The carcass has the same specifications for the number of plies (1), cord (polyethylene terephthalate; 1670 dtex / 2), cord angle (90 degrees), and cord density (50 / 5cm). The belt layer has the same specifications with the number of plies (2), cord (steel; 1 × 3 / 0.27), cord angle (+ 20 ° / −20 °), and cord density (40 / 5cm). The band layer is formed of a single band ply of a full band obtained by spirally winding a band-like ply having a width of 10 mm and a cord density (49/5 cm) using the band cords shown in Table 1.
[0034]
(1) Road noise;
A sample tire attached to all wheels of a passenger car (1800cc) under internal pressure (200kPa), running a smooth road surface test course for road noise evaluation at a speed of 80km / h, and attached to the driver's seat Using a sound microphone, the noise level (dB) of the 250 Hz band was measured. The measurement results were displayed as an index with Comparative Example 1 as 100. The smaller the value, the lower the road noise and the better.
[0035]
(2) Durability;
Using a drum testing machine, the test tire was run at a speed of 80 km / h under load (load of 150% of the maximum load according to JIS) and internal pressure (internal pressure of 80% of the internal pressure specified in JIS). The distance traveled was measured. The measurement results were displayed as an index with Comparative Example 1 as 100. The larger the value, the better the durability and the better.
[0036]
[Table 1]

[0037]
It can be confirmed that the embodiment can significantly reduce road noise while maintaining or improving durability.
[0038]
【The invention's effect】
As described above, the pneumatic tire of the present invention is made of polyethylene 2,6 naphthalate in which the cord thickness, the number of twists, the initial modulus and the rate of change in the temperature range of 25 ° C. to 70 ° C. are specified as the band cord. Since the fiber cord is used, the road noise reduction effect can be more effectively exhibited while ensuring the durability.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a tire showing an embodiment of the invention.
FIG. 2 is a perspective view showing a structure of a belt-like ply.
[Explanation of symbols]
2 Tread portion 6 Carcass 7 Belt layer 9 Band layer 10 Band cord 9A Band ply 14 Polyethylene 2,6 naphthalate fiber cord

Claims (2)

A pneumatic radial tire comprising a belt layer arranged inside the tread and outside the carcass, and a band layer arranged outside the belt layer,
The band layer is composed of one or more band plies in which the band cord is spirally wound at an angle of 5 degrees or less with respect to the tire circumferential direction, and the band cord has a cord thickness of 2500 to 3600d, While using a polyethylene 2,6 naphthalate fiber cord having a twist number of 30 to 35 times / 10 cm,
The polyethylene 2,6 naphthalate fiber cord has an initial modulus at 25 ° C. of 50 to 65 gf / d and a rate of change of the initial modulus between 25 ° C. and 70 ° C. within ± 20%. Radial tire.   The pneumatic radial tire according to claim 1, wherein the polyethylene 2,6 naphthalate fiber cord has a cord elongation of 0.5 to 2.5% at a load of 2.0 gf / d.

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