JP2002225508A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic radial tire which reduces medium frequency road noises as well as maintaining a high speed endurance even being used under a high humidity. SOLUTION: As a reinforcing fiber cord of a belt cover layer 6, an acrylic fiber-based cord fA with 4.5 cN/dtex or more of expansion strength and 2.0-4.5% of expansion at a load of 2.0 cN/dtex and a fiber cord fB made of at least one kind selected from nylon, polyester, and rayon and used, or an acrylic fiber with the above physical characteristics and a fiber cord fAB made by filament combining or twisting at least one kind of fiber selected from nylon, polyester, and rayon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire, and more particularly to a pneumatic radial tire.
Hz) and a pneumatic radial tire with improved high-speed durability.

[0002]

2. Description of the Related Art Conventionally, a pneumatic radial tire for high-speed running has a belt layer made of a steel cord, and a nylon fiber cord is disposed substantially at 0 ° with respect to the circumferential direction of the tire at both ends or the entire surface of the belt layer. By providing a belt cover layer that is continuously wound so as to increase the hugging effect on the belt layer, high-speed durability is enhanced, and thereby an effect of reducing medium-frequency road noise is obtained. . Here, the road noise is a resonance sound generated when a vibration picked up by the tires on the road surface during high-speed running resonates in the vehicle interior through the axle.

The present inventors have previously described Japanese Patent Application No. 11-16140.
No. 7 proposed a pneumatic radial tire in which medium frequency road noise can be further improved by using an acrylic fiber cord having specific physical characteristics instead of the nylon fiber cord. However, the pneumatic radial tire has a problem that the acrylic fiber cord deteriorates when used for a long time in a high humidity environment, and the high-speed durability gradually decreases, and there is still room for improvement.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a method for forming a belt cover layer with an acrylic fiber cord.
It is an object of the present invention to provide a pneumatic radial tire capable of reducing medium-frequency road noise while maintaining high-speed durability even when used under high humidity.

[0005]

According to the pneumatic radial tire of the present invention that achieves the above object, a belt layer is provided outside a carcass layer in a tread, and a tension layer is provided at least outside both ends in the tire width direction of the belt layer. 4.5 cN strength
/ Dtex or more, and an acrylic fiber cord having an elongation of 2.0 to 4.5% under a load of 2.0 cN / dtex, and at least one fiber cord selected from nylon, polyester and rayon. A belt cover layer wound substantially at an angle of 0 degrees in the circumferential direction is provided.

In place of the above structure, the cord of the belt cover layer has a tensile strength of 4.5 cN / dtex or more and an elongation under a load of 2.0 cN / dtex of 2.0 to 4.5.
% Of an acrylic fiber and at least one fiber selected from nylon, polyester and rayon.

The acrylic fiber or its cord has a tensile strength of 4.5 cN / dtex or more and 2.0 cN / dt.
Since the elongation at the time of ex load is 2.0 to 4.5%, the elastic modulus is higher than that of the conventional nylon fiber cord, so that the circumferential rigidity at both ends in the tire width direction of the belt layer is further increased. In addition, the deformation mode (second section mode) in which the tire section vibrates in the same phase in the tread section and the side wall section and the shoulder section vibrates in the opposite phase due to the vibration during tire running is suppressed, and the intermediate frequency road noise is reduced. It becomes possible. Similarly, the binding force at the end of the belt layer is further improved, and the high-speed durability can be improved.

[0008] Further, in addition to the above-mentioned acrylic fiber or its cord, at least one fiber cord selected from nylon, polyester and rayon, which is more excellent in resistance to moisture absorption and deterioration, is used in combination with the belt cover layer. Therefore, high-speed durability can be maintained even when the acrylic fiber is deteriorated by use under high humidity.

[0009]

FIG. 1 shows a first embodiment of a pneumatic radial tire according to the present invention.

In FIG. 1, a carcass layer 2 is mounted so as to extend from a tread 4 to right and left bead portions 1, 1, and both end portions in the tire width direction are turned around a bead core 3 from inside to outside of the tire. ing.

On the outer periphery of the carcass layer, there are disposed two belt layers 5, 5 such that reinforcing cords intersect each other between the layers. The cord angles of the belt layers 5, 5 with respect to the tire circumferential direction are set in the range of 10 to 45 °, preferably 15 to 35 °. As the reinforcing cord, a steel cord is generally used, but an organic fiber cord having a high elastic modulus such as an aromatic polyamide fiber can also be used.

Acrylic fiber cords f _A and nylon fiber cords f _B are alternately arranged one by one at both ends on the outer peripheral side of the belt layers 5, 5, and substantially zero in the tire circumferential direction.
°, more specifically, a belt cover layer 6 formed by being spirally wound at an inclination angle of 5 ° or less.
The fiber cords f _B, may be used a polyester fiber cord or rayon cord. Or,
The fiber cords f _B may be used in combination of two or more of the three types. Also, the fiber cord f _A and f _B, rather than alternately one by one as shown, may be a plurality present are alternately arranged.

[0013] While the embodiment of Figure 1 the belt cover layer 6 shows an example of the edge covering type disposed only at both ends of the belt layer 5, at least an acrylic fiber cord f _A covers the end portion of the belt layer 5 With this configuration, the belt cover layer 6 may be a full cover type that covers the entire width of the belt layer 5.

[0014] FIG. 2 (a) while forming a full cover type belt cover layer 6b of nylon fiber cords f _B, covering the belt cover layer 6a made of acrylic fiber cord f _A both end portions of the belt layer 5 only It is an edge cover.

FIG. 2B shows a belt cover layer 6a made of an acrylic fiber cord f _A and a belt cover layer 6b made of a nylon fiber cord f _B independently of each other, and only covering both ends of the belt layer 5. It was made.

[0016] FIG. 2 (a), (b) In any case, the Toka using the polyester fiber cord or rayon cord as a fiber cord f _B of the belt cover layer 6b, or nylon, polyester, among the three types of rayon From 2
It is the same as in the case of FIG. 1 that more than one species may be used.

FIG. 2 (c) shows an example in which the fiber cord f _AB constituting the belt cover layer 6 is a cord obtained by mixing or twisting acrylic fibers and nylon fibers. Polyester fiber or rayon fiber may be used instead of nylon fiber. Further, the belt cover layer 6 may be a full cover or an edge cover.

However, the acrylic fiber in the fiber cord f _AB has a tensile strength of 4.5 cN / dtex or more,
And the elongation under a 2.0 cN / dtex load is 2.0-4.
5% is used. The higher the tensile strength, the better, but since it is a characteristic relative to the elongation, the upper limit is inevitably determined from the lower limit of 2.0% of the elongation.

In the belt cover layer, the ratio of the acrylic fiber having the above characteristics or the cord thereof is 15 to 85.
%, More preferably in the range of 20 to 80% by weight. When the ratio of the acrylic fiber or its cord is less than 15% by weight, the effect of reducing the intermediate frequency road noise is reduced. If it exceeds 85% by weight, the moisture absorption deterioration of the acrylic fiber becomes conspicuous, and the high-speed durability in a moisture absorbing environment is reduced.

In the present invention, in order to obtain an acrylic fiber having the above characteristics or a cord thereof, an acrylic fiber having an acrylonitrile content of 40 to 100% by weight is used, and the acrylic fiber cord is embedded in rubber. Prior to this, it is preferable to perform the following dipping and heat treatment.

That is, first, an aqueous mixture (RFL) of an initial condensate (RF) of resorcinol (R) and formalin (F) and a rubber latex (L) is dipped, and RFL is attached to the acrylic fiber cord. Aqueous mixture (RFL)
In the above, the weight ratio RF / L of the initial condensate (RF) and the rubber latex (L) is 0.25 to 0.35, and the molar ratio R / F of resorcinol (R) to formalin (F) is 0.28 to
A range of 0.67 is preferred. The type of rubber latex can be appropriately selected depending on the type of unvulcanized rubber in which the acrylic fibers are embedded.

Next, the cord having the RFL attached thereto is dried at, for example, 80 to 150 ° C., and then dried at 150 to 20 ° C.
Heat set (thermal stretching) treatment at 0 ° C.,
A normalizing (relaxation) treatment is performed at 200 ° C. The heat set tension (HS) is HS ≧ 0.175 cN /
dtex, normalizing tension (NL) is NL ≦
It is preferable to set 0.175 N / dtex and HS ≧ NL.

Here, the heat setting treatment means an operation of drawing while heating the fiber (heat drawing treatment). This is to complete the RFL reaction and to increase the dimensional stability and strength of the cord. The normalizing (relaxation) treatment refers to a second treatment performed at a temperature equal to or slightly lower than the tension of the heat set in order to remove fiber distortion generated during heat drawing by heat setting.

By performing the treatment under the above conditions, the tensile strength is not less than 4.5 cN / dtex and 2.0 cN / dtex.
An acrylic fiber cord having an elongation at dtex load of 2.0 to 4.5% is obtained.

[0025]

Examples 1-5, Conventional Example, Comparative Example 1 The tire structure, tire size, reinforcing cords of the belt layer and the belt cover layer were made common as follows, and an acrylic fiber cord and a nylon fiber cord of the belt cover layer were used. Of the pneumatic radial tires of Examples 1 to 5, the conventional example, and the comparative example 1 in which the compounding ratios of the tires were different as shown in Table 1.

Tire structure: FIG. 1 Tire size: 195 / 65R15 Belt layer: 2 layers of 1 × 3 × 0.30 brass-plated steel cord, number of ends 32/50 mm, cord angle (with respect to tire circumferential direction) Upper layer + 24 °, lower layer −24 ° Belt cover layer: acrylic fiber cord (tensile strength 5.
0 cN / dtex, intermediate elongation (2.0 cN / dtex)
3.0%) and a combination of nylon fiber cords The seven types of tires obtained as described above were each measured for medium-frequency road noise and high-speed durability after exposure to high humidity by the following measurement methods. 1 was obtained.

Measurement of medium frequency road noise: rim size 1
A test tire with a 5 x 6JJ rim and internal pressure of 200 kPa was mounted on an FR car with a displacement of 3.0 liters, and was run on a road noise measurement road at a speed of 50 km / h. A sound collecting microphone was installed, and the road noise sound pressure at a frequency of 315 Hz was measured. The evaluation results are shown as an index with the sound pressure level of the conventional tire being 100. The higher the value, the better the effect of reducing the mid-frequency road noise.

Measurement of high-speed durability after high-humidity exposure: A test tire assembled into a rim having a rim size of 15 × 6JJ at an internal pressure of 220 kPa was held for 30 days in a chamber maintained at a room temperature of 70 ° C. and a relative humidity of 95%. 1707m in diameter
m, using a drum tester with an ambient temperature of 38 ± 3 ° C., a load of 541 kg (Japanese Automobile Tire Association Standard JAT
Under the condition of 88% of the maximum load specified in MA1999), the vehicle was run at an initial speed of 121 km / h at an interval of 8 km / h every 30 minutes until the tire was broken. The total mileage up to destruction was indicated by an index with the conventional tire set to 100. The higher the value, the better the high-speed durability under a moisture absorbing environment.

[0029]

[Table 1] As is clear from Table 1, as the reinforcing cord for the belt cover layer, the tensile strength is 4.5 cN / dtex or more, and the elongation under 2.0 cN / dtex load is 2.0 to 4.5%.
The tires of the examples using the nylon fiber cord with the blend ratio of the acrylic fiber cord of 15 to 85% of the present invention all improved the medium frequency road noise while maintaining the high-speed durability even after exposure to high humidity. Understand.

Examples 6 and 7, Comparative Example 2 The tires of Example 3 described above were identical except that the tensile strength and intermediate elongation of the acrylic fiber cord used for the belt cover layer were different as shown in Table 2. Three types of tires were manufactured under the conditions.

For these three types of tires, the medium frequency road noise and the high-speed durability after exposure to high humidity were measured by the same measurement method as described above. The results shown in Table 2 were obtained.

[0032]

[Table 2] As is clear from Table 2, the acrylic fiber cord has a tensile strength of 4.5 cN / dtex or more and 2.0 cN / dt.
It can be seen that when the one having an elongation at the time of ex load of 2.0 to 4.5% is used, the high-speed durability and the medium frequency road noise are improved.

[0033]

As described above, according to the pneumatic radial tire of the present invention, middle frequency road noise can be reduced while maintaining high-speed durability even when used under high humidity.

[Brief description of the drawings]

FIG. 1 is a meridian half sectional view showing one embodiment of a pneumatic radial tire of the present invention.

FIGS. 2 (a), (b), and (c) are explanatory views illustrating other embodiments of the structure of the belt cover layer in the pneumatic radial tire of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Bead part 2 Carcass 3 Bead core 4 Tread part 5 Belt layer 6, 6a, 6b Belt cover layer f _A acrylic fiber cord f _B nylon fiber cord f _AB mixed or twisted cord

Claims (6)

[Claims] 1. A belt layer is provided outside a carcass layer in a tread, and a tensile strength of at least 4.5 cN / dtex and a load of 2.0 cN / dtex is provided at least outside both ends in the tire width direction of the belt layer. 2.0 elongation
Pneumatic with a belt cover layer in which an acrylic fiber cord of 4.5% and at least one kind of fiber cord selected from nylon, polyester and rayon are wound at an angle of substantially 0 degree in the tire circumferential direction. Radial tire. 2. The belt cover layer according to claim 1, wherein the belt cover layer made of the acrylic fiber cord and the belt cover layer made of at least one fiber cord selected from the group consisting of nylon, polyester and rayon are arranged independently of each other. Pneumatic radial tire. 3. The belt cover layer according to claim 1, wherein the acrylic fiber cords and the at least one kind of fiber cords selected from nylon, polyester and rayon are alternately arranged every one or several cords. The pneumatic radial tire according to 1. 4. The fiber cord constituting the belt cover layer, wherein the ratio of the acrylic fiber cord is 15 to 8;
The pneumatic radial tire according to claim 1, wherein the content is 5% by weight. 5. A belt layer is provided outside a carcass layer in a tread, and a tensile strength of at least 4.5 cN / dtex and a load of 2.0 cN / dtex is provided at least outside both ends in the tire width direction of the belt layer. 2.0 elongation
A fiber cord made of a blended or twisted mixture of 4.5% acrylic fiber and at least one fiber selected from nylon, polyester and rayon was wound at an angle of substantially 0 ° in the tire circumferential direction. Pneumatic radial tire with a belt cover layer. 6. The pneumatic radial tire according to claim 5, wherein a blending ratio of the acrylic fiber in the fiber cord is 15 to 85% by weight.