JPH11240311A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce tire noise by arranging a belt reinforcing layer parallely in a circumferential direction of the tire while spirally winding fiber codes around which the belt reinforcing layer is spirally wound. SOLUTION: A narrow and lengthy rubber/code compound is prepared by spirally winding a belt reinforcing layer 5 around a plurality of fiber codes, followed by rubber coating. The rubber/code compund is spirally wound in a circumferencial direction. In such a rubber/code compund, the belt reinforcing layer 5 is improved in both its rigidity and extendability. Tread portions 3 near both ends of a belt layer 4 are improved in rigidity by adopting highly elastic fibers, and arranging the highly elastic belt reinforcing layers 5 at least near both endgs of the belt layer 4. Oscillation of the tread portions 3 can thus be reduced at the portion near both ends of the belt layer 4, and tire noise can also be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a pneumatic radial tire, and more particularly to a pneumatic radial tire with significantly reduced tire noise.

[0002]

2. Description of the Related Art In recent years, with the advancement of high-grade and high-quality vehicles, especially in passenger cars, low vibration of vehicles and improvement of ride comfort are rapidly progressing. There is a demand for noise reduction, and in particular, reduction of noise transmitted to the interior of the vehicle is desired. As one of such noises, there is a noise generated due to vibration of the tread portion when the tread portion of the tire leaves the road surface, and it is known that this noise is generated at a location where the rigidity of the tread portion is low. Have been. As a method of reducing such tire noise, a method of softening rubber in a tire tread portion has been conventionally attempted. However, in this method, even if the tire noise can be reduced by softening the rubber in the tread portion, the wear resistance is greatly reduced, and the steering stability is inevitably greatly reduced, and is not practical. Absent.

[0003] Therefore, a method of improving the rigidity of the tread portion by providing a belt reinforcing layer in which fiber cords are arranged in the tire circumferential direction near the low rigidity portion of the tread portion, ie, near both ends of the belt layer, is considered. Can be In this case, in order to increase the rigidity, it is necessary to use a high elastic fiber such as aramid fiber. However, since such high-elasticity fibers usually tend to have extremely low elongation, if high-elasticity fibers are used for the belt reinforcing layer, the raw tire before vulcanization in the mold at the time of tire vulcanization is obtained. If it does not expand sufficiently, it does not adhere to the inner surface of the mold, and molding failure may occur. Therefore, in order to avoid such molding failure, only low-elasticity fibers that allow elongation required for expansion can be used, and the actual situation is that tire noise has not been reduced.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pneumatic radial tire in which the tire noise is significantly reduced without causing problems such as molding failure during tire production. It is the purpose.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies to develop a pneumatic radial tire with significantly reduced tire noise without causing problems such as molding failure during tire manufacturing. It has been found that the object can be achieved by covering at least both ends of the belt layer with a belt reinforcing layer using a specific cord. The present invention has been completed based on such findings. That is, the present invention provides a pair of bead portions, a toroidal carcass extending over both bead portions, a tread portion located at a crown portion of the carcass, and a belt layer disposed inside the tread portion, In a radial tire having a belt reinforcing layer covering at least both end portions of the belt layer, the belt reinforcing layer is formed by spirally winding a helically shaped fiber cord so as to be substantially parallel to a tire circumferential direction. The present invention provides a pneumatic radial tire characterized by being formed by:

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of a pneumatic radial tire according to the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing an example of a pneumatic radial tire according to the present invention. A carcass 2 which is folded back and locked, a tread portion 3 located at a crown portion of the carcass 2, at least two belt layers 4 arranged inside the tread portion 3, and both end portions of the belt layer 4. 2 shows a structure provided with a belt reinforcing layer 5 to cover. In the pneumatic radial tire of the present invention, each of the bead portion, the carcass, the tread portion, and the belt layer is not particularly limited, and may have a known material and structure conventionally used in a pneumatic radial tire. However, the belt reinforcing layer covers at least both end portions of the belt layer and needs to be formed as described below.

Here, the belt reinforcing layer is formed by rubberizing one or a plurality of parallel cords of a helically shaped fiber cord into a long narrow rubber / cord composite having a predetermined narrow width. This is formed by spirally winding this in the tire circumferential direction. Such rubber /
Since the cord composite is extensible in its longitudinal direction (tire circumferential direction), even if the fiber itself constituting the cord composite has high elasticity and low cutting elongation, it is hardened in the mold during vulcanization molding. Is sufficiently expanded in the longitudinal direction. That is, even if the belt reinforcing layer itself is set to have high elasticity, the elongation of the belt reinforcing layer itself can be increased. Therefore, the high elasticity fiber is used, and the high elasticity belt reinforcing layer is formed at least at both ends of the belt layer. By arranging the tread portion near the portion, the rigidity of the tread portion near both end portions of the belt layer can be increased. As a result, the vibration of the tread near the both ends of the belt layer can be reduced, and the tire noise can be significantly reduced. Further, since the belt reinforcing layer itself has high elongation even if it has high elasticity, even if a fiber cord having high elasticity and low elongation is used, the fiber cord is not cut during vulcanization molding, Since the green tire can be sufficiently expanded with a margin, tire molding defects do not occur. It is needless to say that the belt reinforcing layer can improve not only the tire noise but also the durability of the end portion of the belt layer.

In the present invention, the elastic modulus of the belt reinforcing layer itself depends on the spiral pitch (P) and the radius (R) of the spirally formed fiber cords constituting the belt reinforcing layer. Therefore, in the present invention, the helical fiber cord has a constant pitch, and R <P /
8 are preferable, and R ≦ P /
Those satisfying 20 are particularly preferable. When R is P / 8 or more, the elastic modulus of the belt reinforcing layer itself does not become sufficiently high, so that reduction in tire noise may not be sufficiently exhibited. In addition, the helical radius of the fiber cord (R)
Can be appropriately selected depending on the tire size. In the case of a radial tire for a passenger car, a tire having a diameter of about 0.15 to 0.40 mm may be used, and a diameter of 0.15 to 0.25 mm is particularly preferable. In this case, the spiral pitch (P) of the cord is
It is about 1.2 mm to 3.2 mm. In addition, the thickness of the fiber cord itself and the number of windings in the tire circumferential direction also affect the tire noise, but these may be appropriately selected according to various situations. The material of the helical fiber cord constituting the belt reinforcing layer used in the present invention is preferably of high elasticity. The high elasticity fiber is not particularly limited, and conventionally known fibers such as steel fiber and aramid fiber Any fiber can be appropriately selected from polybenzoxazole fiber, carbon fiber, glass fiber, or a composite fiber thereof, and a steel fiber is particularly preferable. Further, the fiber cord used for shaping into a helical shape used in the present invention may be a monofilament, or may be a multifilament or a twisted cord obtained by twisting a plurality of strands. Single wires are preferred. In addition,
The belt reinforcing layer of the radial tire according to the present invention is obtained by forming a narrow, long rubber / cord composite obtained by rubberizing such a helically shaped fiber cord at both ends of the tire belt. It is manufactured by spirally winding the tire in the circumferential direction, but there is no particular limitation on the rubberizing method and the winding method, and a conventionally known method can be used.

[0009]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The tire noise level was measured according to the following method. <Tire noise level> Using a drum tester with an outer diameter of 3 m having irregularities on the surface, controlling the ambient temperature to 30 ± 3 ° C, and following the method specified in JIS D4230 (1986) 5, 3, 1 After mounting on the rim, fill the internal pressure, JA
The noise level (100 Hz to 400 Hz) at a running speed of 60 km / hr was measured under the maximum load capacity at the corresponding air pressure in the TMA standard (1996).

Examples 1 to 6 and Comparative Example 1 The tires in Examples and Comparative Examples were all tire size 195 / 65R14, and the carcass cord was a tire using polyethylene terephthalate (PET).
In the production of this tire, vulcanization conditions were 180 ° C. × 13 minutes, post cure inflation conditions were an internal pressure of 0.25 MPa,
The test was performed at a setting of 26 minutes. The tire structures manufactured here are all the same tubeless structure, the belt is a steel belt and has two layers, the steel cord is 1 × 5 × 0.23 structure, the number of shots is 34.0 / 5cm, The angle of the first belt layer was 22 degrees left with respect to the circumferential direction, and the angle of the second belt layer was 22 degrees right with respect to the circumferential direction. The belt reinforcement layer has a diameter of 0.2 on both ends of the belt layer.
It was formed by winding a 5 mm steel single wire spirally 20 times in the tire circumferential direction. Each radial tire using the helical fiber cord as shown in Table 1 for the belt reinforcing layer was manufactured by the above method, and the tire noise level of the obtained tire was evaluated by the test method described above. Table 1 shows the results. Comparative Example 1 A pneumatic radial tire was manufactured in the same manner as in the example except that the belt reinforcing layer was not provided, and the tire noise level was measured. The results are shown in Table 1.

[0011]

[Table 1]

From Table 1, it can be seen that the tires of the examples have lower tire noise levels than the tires of Comparative Example 1, and
In particular, in Examples 1 to 4, it can be seen that the improvement effect is remarkable. Note that the tires of Examples 5 and 6 have R <P / 8
Is not satisfied, the tire noise level is slightly higher than in the other examples.

[0013]

According to the pneumatic radial tire of the present invention, the belt reinforcing layer is formed by spirally winding a helically shaped fiber cord so as to be substantially parallel to the tire circumferential direction. In addition, the tire noise can be greatly reduced without the problem of poor molding at the time of tire production and other adverse effects such as abrasion resistance and steering stability of the product tire.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of an example of a pneumatic radial tire of the present invention.

[Explanation of symbols]

 1: bead core 2: carcass 3: tread 4: belt layer 5: belt reinforcing layer

Claims (3)

[Claims] 1. A pair of bead portions, a toroidal carcass extending over both bead portions, a tread portion located at a crown portion of the carcass, and a belt layer disposed inside the tread portion. In a radial tire having a belt reinforcing layer covering both end portions of the belt layer, the belt reinforcing layer is formed by spirally winding a helically shaped fiber cord so as to be substantially parallel to the tire circumferential direction. A pneumatic radial tire characterized by being formed. 2. The pneumatic radial tire according to claim 1, wherein the helically shaped fiber cords in the belt reinforcing layer have a constant pitch. 3. The helically shaped fiber cord in the belt reinforcing layer satisfies the relationship of R <P / 8, where the helical pitch is P and the helical radius is R. Item 4. A pneumatic radial tire according to item 2.