JPH0930217A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lighten tire weight by making the total length joining the thickness center of a reinforcement cord layer on the tire cross section within a specific percentage of a carcass maximum cross section height, making a cord within the range of specific counts, and separately arranging the cords within the layer as a cord group brought together within a specific range along the surface of the reinforcement cord layer. SOLUTION: The total length joining the thickness center of a reinforcement cord layer 7 (the length between the outer side end P and the inner side end Q in the tire radius direction) is made within the range of 20 to 70% of the maximum height Hc of a carcass 5 when it is measured from a perpendicular line BLc to a tire equator surface E which passes through the minimum diameter at the portion where the carcass 5 bead core 4 is wound up. Cord counts of reinforcement cord layer 7 inside the tire are made within the range of 20 to 60 pieces per 5cm. The reinforcement cord layer 7 cords are separately arranged inside the layer 7 within the range of 2 to 5 along the layer 7 surface as a cord group putting cords together. By composing it in such a manner, operational stability performance can be largely improved upon maintaining sufficient endurance performance.

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 sidewall reinforcing cord layer effective for improving the performance of a pneumatic radial tire for passenger cars, while maintaining excellent steering stability at a high level. Relates to a pneumatic radial tire with significantly improved durability performance.

[0002]

2. Description of the Related Art Applying a reinforcing cord layer to a sidewall portion is widely practiced as an effective means for improving the steering stability of a pneumatic radial tire for passenger cars. Steel cords and organic fiber cords are generally applied to this reinforcing cord layer.

Certainly, the radial tire to which the above-mentioned reinforcing cord layer is applied has tire rigidity further improved as compared with a tire not using the reinforcing cord layer. As a result, steering stability performance is improved, but durability performance is also deteriorated. To be forced. It is known that this deterioration in performance is caused by the reinforcing cord layer.

[0004]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a pneumatic radial tire capable of improving steering stability performance without lowering durability performance.

[0005]

In order to achieve the above object, a pneumatic radial tire of the present invention comprises a pair of bead portions and a pair of sidewall portions, and a tread portion continuous in a toroidal shape between these sidewall portions. Which has a radial carcass of 1 ply or more to reinforce the bead cores embedded in the bead part, and a belt to reinforce the tread part, and a rubberized reinforcing cord layer outside the carcass in the sidewall part region. In the provided pneumatic radial tire, the total length of the line connecting the thickness centers of the reinforcing cord layers in the tire cross section is within the range of 20 to 70% of the carcass maximum sectional height, and the cord of the reinforcing cord layer is struck per 5 cm. 20 to 60 included
The number of cords is within the range of the book, and the cords are grouped within the range of 2 to 5 along the surface of the reinforcing cord layer and are separated and arranged in the layer.

In carrying out the present invention, the cord weave cord used in the above-mentioned reinforcing cord layer has two to five cords adjacent to each other of the cord as a unit, and a weft thread is passed on the same side in the unit cord, A cord group of the reinforcing cord layer is formed by weaving a weft yarn on the opposite side between the adjacent cord units, and the cord of the reinforcing cord layer is 40 to 80 ° with respect to the tire radial direction.
It is desirable to arrange at an inclination angle within the range.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to FIGS. FIG. 1 is a diagram schematically showing a left half section from an equatorial plane E of a pneumatic radial tire, in which 1 is a pair of bead portions (only one side is shown) and 2 is a pair of sidewall portions ( 3 is a tread portion, and a radial carcass 5 of 1 ply or more (two plies in the illustrated example) is provided between the bead cores 4 embedded in the bead portion 1, and the bead portion 1, the sidewall portion 2 and the tread portion are provided. The belt 6 reinforces the tread portion 3 on the outer circumference of the carcass 5. The belt 6 has at least two non-stretchable cord intersecting layers, for example, steel cord intersecting layers.

A rubberized reinforcing cord layer 7 is arranged in the side wall region 2 outside the carcass 5. Although the arrangement shown is an example of the outside of the folded-back portion 5a of the carcass 5, the reinforcing cord layer 7 is provided inside the folded-back portion 5a and the bead filler rubber 8.
The carcass 5 and the inside of the bead filler rubber 8 may be positioned between the carcass 5 and the inside of the bead filler rubber 8.

In FIG. 1, the total length of the line connecting the thickness centers of the reinforcing cord layers 7 (the length between the outer end P and the inner end Q in the tire radial direction) is the portion at which the bead core 4 of the carcass 5 is rolled up. BL to the tire equatorial plane E passing through the minimum diameter of
Maximum carcass 5, measured from _C 20 to 70% of the height H _C
It is necessary to be within the range of. Because, if it is less than 20%, the function as the reinforcing cord layer cannot be sufficiently exerted, and if it exceeds 70%, the deformation near the upper end of the reinforcing cord layer 7 when the tire is loaded becomes local and the strain becomes large. This is because the durability of the tire cannot be maintained.

It is desirable that the inner end Q of the reinforcing cord layer 7 is located outside the outer peripheral surface of the bead core 4 in the tire radial direction (hereinafter referred to as the radial direction). Regarding the steering stability performance and the durability performance, depending on the total length of the reinforcing cord layer 7, there is a tendency that arranging the reinforcing cord layer 7 on the outer side in the radial direction contributes to further improvement of the steering stability performance. Placing it more inward is advantageous for improving the durability performance of the reinforcing cord layer.

The number of cords to be struck in the tire of the reinforcing cord layer 7 is within the range of 20 to 60 cords per 5 cm. If it is less than 20, the cord cannot serve as a reinforcing cord layer, and if it exceeds 60, it is disadvantageous in maintaining durability.

After the number of cords is set within the above range, the cord of the reinforcing cord layer 7 is further divided into two along the surface of the layer 7.
Within the range of up to 5 cords, the cords are collectively arranged as a cord group in the layer 7. If the number of cords in the cord group exceeds 5, a disadvantage of deterioration in tire durability due to deterioration in separation at the cord ends occurs, so the upper limit is set to 5. Figure 2 (a) and (b) of the above-mentioned separated arrangement
Shown in 2A and 2B are views showing only the cord portion of the reinforcing cord layer 7 which is to be embedded in rubber in the cross section taken along the line AA shown in FIG. 1 and omitting the other portions. .

In FIGS. 2A and 2B, the code C is a
The symbol G_n-1, G_n, G _{n + 1}, G_{n + 2}Is it
The code groups are shown below. Code group G shown in FIG._n-1
~ G _{n + 2}Each consists of two cords C, as shown in FIG.
Code group G shown in (b)_n-1~ G _{n + 1}Each has three
It consists of code C. As is clear from the figure, the same code
The cords C in the group are in contact with or close to each other.
While in a state, each code group G_n-1, G_n, G_{n + 1}, G
_{n + 2}Are separated from each other through rubber.

The code group having the above separated arrangement is obtained by the method described below. That is, the rubberized cord layer as a reinforcing member of the tire is almost entirely manufactured from a cord weave cord, and this cord uses weft yarns (weft yarns) for aligning cords (that is, warp yarns) in the width direction. Since this weft yarn is a yarn for exclusively aligning warp yarns, the weft yarn is roughly driven, and is thinner and thinner than the thickness and strength of the cord.
A 400 denier cotton thread or the like is used. This weft is shown with reference numeral Ls in FIGS. 2 (a) and 2 (b).

Therefore, in manufacturing the cord weave cord cloth,
With 2 to 5 cords that are adjacent to each other as a unit,
That is, in the example of FIG._n-1, G_n,
G_{n + 1}, G _{n + 2}In the same code group as
Then, pass the wefts Ls on the same side and adjoin each other.
On the other side, pass the weft yarn Ls on the opposite side
By weaving, the cord shown in FIGS. 2 (a) and 2 (b) is obtained.
It is possible to obtain a group arrangement. In contrast, conventional reinforcement
The code layer is a code layer as shown in FIG.
The cord arrangement is such that weft yarns Ls are alternately passed through for each C
You.

When the tire rolls under a load, a large shear strain acts on the radially outer end P of the reinforcing cord layer 7 located in the ground contact surface, more precisely, the outer end P of the cord end. . This is the same as in the case of conventional tires, and the shear strain acting on the radially outer cord ends of the conventional reinforcing cord layer is disadvantageous in strain relaxation due to rubber due to the narrow mutual cord spacing, and as a result, the rubber cord is A crack is generated, which progresses and leads to a separation failure, which inevitably results in deterioration of durability performance.

On the other hand, in the arrangement of cord groups as shown in FIGS. 2A and 2B, the cord groups G _n-1 , G _n , G _n , G _{n + 1} , G
The mutual spacing of each of _{n + 2} is greatly expanded as compared with the conventional one, and as a result, the shear strain of the cord end located at the end of the cord group among the cord ends of the outer end P is greatly relaxed. Therefore, the generation of rubber cracks at the cord end is suppressed, and the durability performance is improved. In addition, it is of course possible to exhibit a very high level of steering stability performance.

Further, the cords of the reinforcing cord layer 7 are arranged at an inclination angle within the range of 40 to 80 ° with respect to the tire radial direction, and the tire rigidity is effectively improved by this cord arrangement, which results in steering stability performance. Contributing to further improvement.

As the cord material of the reinforcing cord layer 7, either an organic fiber cord such as nylon or polyester or an inorganic fiber cord such as glass or carbon is suitable, and among them, a polyester fiber which is widely used for the ply of the carcass 5. The cord is suitable and the rubber applied to the reinforcing cord layer 7 is preferably the same as the ply rubber of the carcass 5.

A pneumatic tire for passenger cars, which is advantageous when the reinforcing cord layer 7 is applied, is a flat tire having a nominal aspect ratio of 70 or less. Particularly, in the case of this tire, a particularly excellent effect is obtained. Demonstrate.

[0021]

EXAMPLE A pneumatic radial tire for passenger cars of size 205 / 65R15, and according to FIG. 1, the carcass 5 has a 1000D / 2 polyester cord ply structure in a 2-ply radial arrangement, and the belt 6 has 2 layers of 1 ×. 5x
Steel cord crossing layer with 0.23 structure (separation structure) and one layer of nylon cord 12 arranged on the outer periphery thereof
A three-layer structure with a circumferential winding layer (not shown) of 60D / 2 was used.

Using the above as common elements, tires of Examples 1 to 3 and tires of Comparative Examples 1 to 6 and conventional tires not using a reinforcing cord layer were prepared as controls. The cord of the reinforcement cord layer has the same 1000 as the ply of the carcass 5.
D / 2 polyester cord C was used. Except for the conventional example, the number of these cords C driven (5/5 cm), the threading method of the weft Ls (the number of cord groups), the inclination angle (degrees) of the cord C with respect to the tire radial direction, and the carcass maximum cross-section height H
Table 1 collectively shows the percentage (%) of the total length L of the reinforcing cord layer with respect to c. In Table 1, in order from the top, the number of warp threads (number of threads / 5 cm), weft threading method (number of groups), warp inclination angle (degree), and L / Hc × 100 (%) are abbreviated.

[0023]

[Table 1]

In order to verify the effect of the embodiment,
Using each of the tires of Comparative Examples 1 to 6 and Conventional Example as test tires, a comparative evaluation test was performed according to the following performance test items and methods. (1) Steering stability: Internal pressure of 2.0 kgf / cm based on the tire rigidity test method as the most reliable substitute characteristic test.
^After fixing the rotation shaft of the tire and wheel assembly filled with ² , the contact surface of the tire with a normal load of JATMA at an internal pressure of 2.0 kgf / cm ² was measured within ± 10 mm in the front and rear and ± 10 mm in the left and right. The rigidity of each tire was calculated by indexing the conventional example tire as 100 by measuring and averaging the ratio of the moving force to the displacement amount when moved in the front-rear and left-right directions. The larger the value, the better. (2) Durability: A tire and wheel assembly filled with an internal pressure of 2.0 kgf / cm ² is pressed against the drum under an excessive load of 150% of the JATMA regular load, run at a specified speed, and run until failure occurs. The distance is shown in index notation with the conventional tire being 100. The larger the value, the better. The results of these tests are shown in the lower column of Table 1.

From Table 1, it can be seen that the tire of the comparative example has the same performance as that of the conventional example. 3, No. With the exception of the tires of No. 5, the durability of the tires was significantly deteriorated at the cost of improved steering stability, resulting in lack of practicality.
It can be seen that the steering stability performance is improved while maintaining the durability performance equal to or higher than that of the conventional example, which is excellent in durability performance.

[0026]

According to the present invention, the insufficient steering stability inherently possessed by the conventional tire having no reinforcing cord layer in the sidewall portion and the conventional tire having the reinforcing cord layer are inherently present. It is possible to provide a pneumatic radial tire capable of simultaneously solving the insufficient durability performance of the above and maintaining a sufficient durability performance and significantly improving the steering stability performance.

[Brief description of drawings]

FIG. 1 is a left half sectional view of a pneumatic radial tire according to the present invention.

FIG. 2 is a cross-sectional explanatory view of a reinforcing cord layer of the present invention.

FIG. 3 is a cross-sectional explanatory view of a conventional reinforcing cord layer.

[Explanation of symbols]

1 bead part 2 sidewall part 3 tread part 4 bead core 5 carcass 5a carcass folding part 6 belt 7 reinforcing cord layer Hc carcass maximum cross section C cord G _n cord group Ls weft

Claims (3)

[Claims] 1. A pair of bead portions, a pair of sidewall portions, and a tread portion which is continuous in a toroidal shape between these sidewall portions, and each portion is reinforced by at least one ply reinforcing bead cores embedded in the bead portion. In a pneumatic radial tire having a radial carcass and a belt that reinforces the tread portion and having a rubberized reinforcing cord layer on the outer side of the carcass in the sidewall region, a line connecting the thickness centers of the reinforcing cord layers in the tire cross section. The total length of the carcass is within the range of 20 to 70% of the maximum cross-section height, and the number of reinforcement cord layers is 20 to 6 per 5 cm.
A pneumatic radial tire characterized in that the number of cords is within the range of 0, and the cords are grouped within the range of 2 to 5 along the surface of the reinforcing cord layer, and are separated and arranged in the layer. 2. The cord weave cord cord used for the reinforcing cord layer is a cord unit in which two to five cords adjacent to each other of the cord cord are used as a unit, and weft yarns are passed on the same side in the unit cord, and cord cords are adjacent to each other. The tire according to claim 1, wherein a cord group of the reinforcing cord layer is formed by weaving a weft yarn on opposite sides of the cords. 3. The tire according to claim 1, wherein the cords of the reinforcing cord layer are arranged at an inclination angle within a range of 40 to 80 ° with respect to the tire radial direction.