JP4149711B2 - Pneumatic radial tire - Google Patents

Description

【００４２】
実施例は、操縦安定性、乗り心地性及び転がり抵抗がバランス良く改善されているのが確認できる。
【００４３】
【発明の効果】
叙上のごとく本発明の空気入りタイヤは、カーカスコードとしてポリエチレン２，６ナフタレート繊維コードを用い、しかもそのコード太さ、撚り数、初期モジュラス、損失正接、並びにこの初期モジュラス、損失正接、動的弾性率の２５℃〜７０℃の温度範囲における変化率を特定しているため、乗り心地性を高く維持しながら操縦安定性を向上できかつ転がり抵抗を低減しうる。
【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。
【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
７ ベルト層
７Ａ、７Ｂ ベルトプライ
９ バンド層
９Ａ バンドプライ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic radial tire excellent in handling stability, ride comfort, and rolling resistance.
[0002]
[Background Art and Problems to be Solved by the Invention]
In general, the performance required for radial tires for passenger cars includes steering stability, ride comfort, fuel efficiency, durability, etc. In order to improve these performances, conventionally, the carcass layer of radial tires for passenger cars has polyethylene terephthalate. Fiber (PET) cords are widely used.
[0003]
However, with the recent upgrade of vehicles, further improvement in performance has been demanded. For this reason, it has been proposed to use a carcass cord having a higher modulus at the initial tension. However, in this case, there is a problem that the ride quality is rather adversely affected because the rigidity of the sidewall portion is increased. It is also important to reduce rolling resistance and improve fuel efficiency on the environment.
[0004]
As a result of the study by the present inventors under such circumstances, polyethylene 2,6 naphthalate fiber cords having specific physical properties are used as carcass cords, and fluctuations in the physical property values in the tire internal temperature range during running are suppressed as much as possible. As a result, it has been found that the driving stability can be improved and the rolling resistance can be reduced while maintaining a high ride comfort.
[0005]
That is, the present invention uses polyethylene 2,6 naphthalate fiber cord as the carcass cord, and the cord thickness, number of twists, initial modulus, loss tangent, and the initial modulus, loss tangent, and dynamic elastic modulus of 25 ° C to 70 ° C. The object of the present invention is to provide a pneumatic radial tire that can improve steering stability and reduce rolling resistance while maintaining high ride comfort, based on specifying the rate of change in the temperature range of ° C.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1 of the present application provides a carcass made of at least one carcass ply extending from a tread portion to a bead core of a bead portion through a sidewall portion, an inner portion of the tread portion and the carcass. A pneumatic radial tire comprising a belt layer formed of a belt ply using at least two steel cords arranged on the outer side in the radial direction of the belt , and a band layer provided outside the belt layer ,
The band layer is formed by spirally winding a tape-like band-shaped ply formed by embedding a single band cord or a plurality of band cords in a topping rubber along the tire circumferential direction,
The carcass ply uses a polyethylene 2,6 naphthalate fiber cord having a cord thickness of 2500 to 3600d and a twist number of 30 to 40 times / 10 cm as a carcass cord,
The polyethylene 2,6 naphthalate fiber cord has an initial modulus of 50 to 65 gf / d, a loss tangent (tan δ) of 0.06 to 0.09, and a dynamic elastic modulus (E *) of 2800 N / cord at 25 ° C. 4000N / cord, and the rate of change of the initial modulus between 25 ° C and 70 ° C, the rate of change of loss tangent (tan δ), and the rate of change of dynamic elastic modulus (E *) are ± 20% or less, respectively.
In addition, the band cord is characterized by using a polyethylene 2,6 naphthalate fiber cord having the same structure as the carcass cord .
[0007]
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%.
[0008]
According to a third aspect of the invention, the polyethylene 2,6 naphthalate fiber cord has 400 to 600 filaments.
[0009]
According to a fourth aspect of the present invention, the tread portion comprises at least one band ply on which the band cord is spirally wound at an angle of 5 degrees or less with respect to the tire circumferential direction on the outer side of the belt layer. A band layer is provided, and the polyethylene 2,6 naphthalate fiber cord is used for the band cord.
[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 extending 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 provided outside the belt layer 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 folded portions 6b that are folded around the bead core 5 on both sides of the ply main body portion 6a straddling the bead cores 5 and 5. Between the ply main body portion 6a and the folded portion 6b, A bead apex rubber 8 for bead reinforcement extending in a radial manner outward from the bead core 5 is disposed.
[0013]
In this embodiment, a polyethylene 2,6 naphthalate fiber cord having a cord thickness of 2500 to 3600 d and a twist number of 30 to 40 times / 10 cm is used as the carcass cord. The number of twists of 30 to 40 times / 10 cm means that the number of lower twists and the number of upper twists are both 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.
[0014]
Here, in order to appropriately obtain a balance between the strength, elongation, and fatigue resistance of the polyethylene 2,6 naphthalate fiber cord, it is important that the number of twists of the cord is 30 to 40 times / 10 cm. If it is less than / 10 cm, the elongation and fatigue resistance become insufficient, and the required cord durability cannot be obtained. If the number of twists exceeds 40 times / 10 cm, the elongation of the cord becomes excessive and it becomes difficult to maintain the tire dimensions.
[0015]
In order to ensure the rigidity and strength of the tire, it is important that the thickness of the polyethylene 2,6 naphthalate fiber cord is 2500 to 3600 d. If it is less than 2500d, the cord is too thin and it is necessary to increase the number of carcass plies, and if it exceeds 3600d, the carcass ply 6A becomes thicker than necessary, which is disadvantageous for weight reduction.
[0016]
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.
[0017]
Since such polyethylene 2,6 naphthalate fibers are highly elastic, the initial modulus at 25 ° C. is 50 to 65 gf / d while maintaining a balance between the strength based on the number of twists, elongation, and fatigue resistance. The dynamic elastic modulus (E *) can be increased to a range of 2800 to 4000 N / cord.
[0018]
The carcass cord is embedded in the tire with an elongation of about 1 to 3% due to stretching during vulcanization molding. Therefore, when considering the tire rigidity and the like due to the carcass cord, this low elongation is The initial modulus M is important. When the initial modulus M is in the range of 50 to 65 gf / d and the dynamic elastic modulus E * is in the range of 2800 to 4000 N / cord, there is a balance between handling stability and ride comfort. Excellent performance can be obtained. When the initial modulus M and the dynamic elastic modulus E * are below the lower limit values of the above ranges, the steering stability is impaired, and when the initial modulus M and the dynamic elastic modulus E * exceed the upper limit values, the riding comfort is impaired.
[0019]
In addition, these physical properties are maintained within the tire temperature range during running so that the fluctuations are kept as small as possible, so that excellent maneuvering stability and riding comfort can be exhibited with high stability. is necessary.
[0020]
Therefore, in this embodiment, the change rate of the initial modulus M and the change rate of the dynamic elastic modulus E * between 25 ° C. and 70 ° C. are further regulated to ± 20% or less, respectively. . That is, when the maximum value and the minimum value of the initial modulus in the temperature range of 25 ° C. to 70 ° C. are Mmax and Mmin, the differences Mmax-M and M-Mmin from the initial modulus M at 25 ° C. are respectively 25 ° C. When the initial modulus M is 20% or less and the maximum and minimum values of the dynamic elastic modulus in the temperature range of 25 ° C. to 70 ° C. are E * max and E * min, the dynamic elastic modulus at 25 ° C. Differences E * max−E * and E * −E * min from E * are set to 20% or less of the dynamic elastic modulus E * at 25 ° C., respectively.
[0021]
In particular, in order to improve the aforementioned handling stability and ride comfort, the rate of change of the initial modulus and the rate of change of the dynamic elastic modulus E * are preferably ± 15% or less, and more preferably ± 10% or less.
[0022]
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.
[0023]
In order to improve handling stability and ride comfort, the number of filaments constituting the polyethylene 2,6 naphthalate fiber cord is preferably 400 to 600. The filament becomes too thick and the ride comfort tends to decrease. Conversely, when it exceeds 600, the filament becomes too thin and the steering stability tends to decrease.
[0024]
From the viewpoint of rolling resistance, it is necessary to reduce the loss tangent (tan δ) of the carcass cord and to suppress the fluctuation as much as possible in the tire internal temperature range during running. Therefore, in this embodiment, as the polyethylene 2,6 naphthalate fiber cord, a loss tangent (tan δ) at 25 ° C. of 0.06 to 0.09 is used, and the loss between 25 ° C. and 70 ° C. is used. The rate of change of tangent (tan δ) is regulated to 20% or less, preferably 15% or less, and more preferably 10% or less.
[0025]
This rate of change is also the same for polyethylene 2,6 naphthalate fiber cords, containing 90% or more of ethylene 2,6-naphthalate units, DSC peak of 280 ° C. or more, intrinsic viscosity of 0.7 or more, and birefringence. By setting the rate to 0.30 or more, it is possible to regulate the above range. 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.
[0026]
Here, the initial modulus M means the inclination at the origin of the “load-elongation” curve of the cord obtained in accordance with the chemical fiber tire cord test method of JIS L1017. The loss tangent (tan δ) and dynamic elastic modulus (E *) of the cord were measured using a viscoelasticity measuring device manufactured by Iwamoto Seisakusho, with frequency (10 Hz), initial load (1000 g / cord), sample length (30 mm), dynamic It is a value measured by strain (0.01 mm).
[0027]
For carcass cords, from the viewpoint of tire dimensional stability, the cord elongation at a load of 2.0 gf / d is preferably in the range of 0.5 to 2.5%. It is disadvantageous for uniformity, such as tending to deteriorate the nature.
[0028]
Next, the belt layer 7, as in the conventional tire, 10 ° steel cord with respect to the tire circumferential direction to 35 ° angle with the inclined arrangement with two the above, two belt plies in this example 7A and 7B. 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. . 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.
[0029]
Also in order to improve the high speed durability suppress lifting of the front Symbol belt layer 7, and the band layer 9 disposed outside of the belt layer 7. The band layer 9 is formed of one or more band plies 9A, in this example, one band ply 9A, in which a band cord is spirally wound at an angle of 5 degrees or less with respect to the tire circumferential direction.
[0030]
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.
[0031]
The band ply 9A uses a tape-like belt-like ply in which one band cord or a plurality of band cord alignment members are embedded in a topping rubber, and this belt-like ply is spirally wound along the tire circumferential direction. It is formed by doing.
[0032]
As the band cord this time, using polyethylene 2,6-naphthalate fiber cord of the carcass cord in the same configuration. In addition, with the same structure, the cord thickness, the number of twists, the initial modulus, the loss tangent, and the dynamic elastic modulus, and the initial modulus between 25 ° C. and 70 ° C., the loss tangent, and the rate of change of the dynamic elastic modulus are Each means within the above-mentioned range, and therefore, other than the completely same code as the carcass code is included.
[0033]
When such a cord is used, the restraining force on the belt layer 7 is increased, and the tagging effect is improved. As a result, the circumferential rigidity of the tread portion 2 becomes large and uniform, and it is difficult to pick up vibrations on the road surface when the tire is running. Therefore, road noise is reduced.
[0034]
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.
[0035]
【Example】
A tire with 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 handling stability, riding comfort, rolling resistance, and road noise characteristics of each sample tire were tested. The results are shown in Table 1.
[0036]
The carcass is formed of one carcass ply having a cord angle (90 degrees) and a cord density (50/5 cm) using the carcass cords shown in Table 1.
The belt layer has the same specifications in terms of the number of plies (2 sheets), 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 in which a band-shaped ply having a width of 10 mm using a band cord and a cord density (49/5 cm) is spirally wound. The same PEN cord (1500d / 2) as the cord is used, and other tires (including comparative examples) use nylon 66 cord (1260d / 2) as the band cord.
[0037]
(1) Steering stability;
A sample tire is mounted on all wheels of a passenger car (1800 cc) under internal pressure (200 kPa), and a tire test on a dry asphalt road surface is performed. Example 1 was evaluated by a 10-point method with 5 points. The larger the value, the better the steering stability.
[0038]
(2) Ride comfort;
Using the vehicle, a test course for ride comfort evaluation was run, and the driver's sensory evaluation was performed with respect to the rugged feeling, the push-up feeling, the damping feeling, etc., and the evaluation was performed by a 10-point method with Comparative Example 1 as 5 points. The higher the number, the better the ride comfort.
[0039]
(3) rolling resistance;
Using the vehicle, after running for 30 minutes at a speed of 80 km / h, release the brake of the car from the 6 m slope with an inclination of 10 °, and measure the distance until the car stops after running naturally. A measurement result is displayed by the index | exponent which set the comparative example 1 to 100, and rolling resistance is so small that a numerical value is large.
[0040]
(4) Road noise;
Using the vehicle, a smooth road surface test course for road noise evaluation was run at a speed of 80 km / h, and a noise level (dB) in a 250 Hz band was measured using a sound collecting microphone attached to the driver's seat. The measurement results are displayed as an index with Comparative Example 1 being 100, and the smaller the numerical value, the lower the road noise and the better.
[0041]
[Table 1]

[0042]
In the embodiment, it can be confirmed that the handling stability, the ride comfort and the rolling resistance are improved in a well-balanced manner.
[0043]
【The invention's effect】
As described above, the pneumatic tire of the present invention uses polyethylene 2,6 naphthalate fiber cord as the carcass cord, and further, the cord thickness, the number of twists, the initial modulus, the loss tangent, and the initial modulus, loss tangent, dynamic Since the rate of change of the elastic modulus in the temperature range of 25 ° C. to 70 ° C. is specified, the driving stability can be improved and the rolling resistance can be reduced while maintaining high riding comfort.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a tire showing an embodiment of the invention.
[Explanation of symbols]
2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 6A Carcass ply 7 Belt layers 7A, 7B Belt ply 9 Band layer 9A Band ply

Claims (4)

A carcass made of at least one carcass ply extending from the tread portion through the sidewall portion to the bead core of the bead portion, and at least two steel cords arranged inside the tread portion and radially outside the carcass are used. A pneumatic radial tire comprising a belt layer composed of a belt ply and a band layer provided outside the belt layer ,
The band layer is formed by spirally winding a tape-like band-shaped ply formed by embedding a single band cord or a plurality of band cords in a topping rubber along the tire circumferential direction,
The carcass ply uses a polyethylene 2,6 naphthalate fiber cord having a cord thickness of 2500 to 3600d and a twist number of 30 to 40 times / 10 cm as a carcass cord,
The polyethylene 2,6 naphthalate fiber cord has an initial modulus of 50 to 65 gf / d, a loss tangent (tan δ) of 0.06 to 0.09, and a dynamic elastic modulus (E *) of 2800 N / cord at 25 ° C. 4000N / cord, and the rate of change of the initial modulus between 25 ° C and 70 ° C, the rate of change of loss tangent (tan δ), and the rate of change of dynamic elastic modulus (E *) are ± 20% or less, respectively. ,
In addition , a pneumatic radial tire is characterized in that the band cord uses a polyethylene 2,6 naphthalate fiber cord having the same configuration as the carcass cord .   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.   The pneumatic radial tire according to claim 1 or 2, wherein the polyethylene 2,6 naphthalate fiber cord has 400 to 600 filaments.   The tread portion includes, on the outside of the belt layer, a band layer made of at least one band ply in which a band cord is spirally wound at an angle of 5 degrees or less with respect to the tire circumferential direction, The pneumatic radial tire according to any one of claims 1 to 3, wherein the polyethylene 2,6 naphthalate fiber cord is used as a band cord.

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