JPH1111112A - Pneumatic raidal tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve belt durability and trail wondering property while ensuring high steering stability. SOLUTION: This pneumatic radial tire comprises two belt layers 7A, 7B having metal cords (f) arranged thereon on the circumference of a carcass layer 4B of a tread part 1, and has a falttening ratio of 0.85 or less. A separating rubber layer 9 for separating the belt layer 7A from the carcass layer 4 (4A, 4B) is arranged in the tread center area between the carcass layer 4B and the belt layer 7A in a width W of 20-45% of a maximum belt width Wb. Its thickness Tc is set larger by 0.3-1.5 mm than the thickness Th of the rubber part between the reinforcing cord of the carcass layer 4B and the metal cords (f) of the belt layer 7A in the middle point P between a tire equatorial line CL and the belt layer end 7a having the maximum belt width Wb.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an aspect ratio of 0.85.
More specifically, the present invention relates to a pneumatic radial tire having improved belt durability and rut wandering.

[0002]

2. Description of the Related Art A pneumatic radial tire in which the cross-sectional shape of a tire is flattened to increase the width of a tread portion has a large tread bending rigidity because a belt layer is also widened according to the tread width. Therefore, the cornering force is large and high steering stability can be obtained.

On the other hand, flat tires for small trucks having an aspect ratio of 0.85 or less have an aspect ratio of 0.95.
There is a problem that the durability and the rut wandering property of the belt layer are reduced as compared with the above tires.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pneumatic radial tire capable of improving belt durability and rut wandering while ensuring high steering stability.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a pneumatic radial tire having an aspect ratio of 0.85 or less, in which two belt layers on which metal cords are arranged are provided on an outer peripheral side of a carcass layer of a tread portion. In the above, a separation rubber layer for separating the belt layer from the carcass layer is arranged in a tread center region between the carcass layer and the belt layer at a width of 20 to 45% of a maximum belt width Wb, and the thickness Tc of the rubber layer is set to The thickness of the rubber portion between the reinforcing cord of the carcass layer and the metal cord of the belt layer at the midpoint position P between the tire equator line CL and the end of the belt layer having the maximum belt width Wb is more than 0.
The thickness is 3 to 1.5 mm.

As described above, the separation rubber layer having the width and the thickness specified in the above-described range is provided in the tread center area between the carcass layer and the belt layer, and the belt layer is separated from the carcass layer in the center area. Thus, when the tire is filled with air pressure, the portion of the belt layer in the center region can be bulged to the outer peripheral side, whereby the metal cord tension of the belt layer in the center region increases, while the shoulder region side has metal. Since the cord tension is small, the shoulder-side rigidity of the tread portion can be reduced. Therefore, the edge separation resistance of the belt layer can be improved, and the tire can easily fall out of the rut. Further, since the bending rigidity of the entire tread can be kept large, the steering stability can be kept high.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 shows an example of a pneumatic radial tire having an aspect ratio of 0.85 or less according to the present invention, wherein 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. Inside the tire, a carcass layer 4 in which reinforcing cords are arranged between the left and right bead portions 3 along the tire width direction.
Are mounted in two layers, and both ends 4a of the inner carcass layer 4A are folded from the inside of the tire with the bead filler 6 sandwiched around the bead core 5 arranged in the bead portion 3 to the outside. Both ends 4b of the outer carcass layer 4B
Extends along the folded back carcass layer end 4a to the vicinity of the bead core 5 outside the tire, so that the bead core 5 is not folded back.

On the outer peripheral side of the carcass layer of the tread portion 1, two belt layers 7 in which metal cords are arranged as reinforcing cords are provided.
Is provided. The two belt layers 7 are arranged so that the metal cords cross each other with the direction of inclination relative to the tire circumferential direction being opposite, and function as tension members. The first belt layer 7A on the inner peripheral side adjacent to the carcass layer 4 is formed wider than the second belt layer 7B disposed on the outer peripheral side thereof. Two belt edge reinforcing layers 8 in which organic fiber cords are arranged in the tire circumferential direction are arranged on both outer peripheral sides of both ends of the belt layer 7.

In the present invention, as shown in detail in FIG. 2, a separation rubber layer 9 is provided in the tread center area between the outer carcass layer 4B and the first belt layer 7A, and the belt layer 7 is provided in the center area. Are separated from the carcass layer 4. The separation rubber layer 9 is disposed in the center region with a width W of 20 to 45% of the maximum belt width Wb which is the width of the first belt layer 7A, and has a thickness Tc having the tire equator line CL and the maximum belt width Wb. Midpoint position P with end of first belt layer 7a
The thickness of the rubber portion 10 between the reinforcing cord of the carcass layer 4B and the metal cord f of the first belt layer 7A at (a distance of 1/4 of the maximum belt width Wb from the tire equator line CL) is 0.3 to 1 more than the thickness Th. .5mm thicker.

By providing the separation rubber layer 9 to separate the belt layer 7 in the center region from the carcass layer 4 rather than the shoulder region, the belt layer portion in the center region is more peripherally positioned than the shoulder region when the internal pressure is filled. It can be bulged to the side. As a result, the tension of the metal cord increases in the center region of the belt layer, but the tension decreases in the shoulder region, whereby the rigidity of the tread portion 1 on the shoulder side can be reduced. Edge separation can be suppressed, and rut wandering can be improved. In addition, since rigidity can be maintained in the entire tread portion, high steering stability can be ensured.

The width W of the separation rubber layer 9 is equal to the maximum belt width W.
If it is less than 20% or more than 45% of b, it is not enough to lower the tension of the metal cord in the shoulder region, so that it is difficult to improve the rut wandering property and to improve the belt durability. Small improvement effect. Width W of separation rubber layer 9
Are 10-2 on each side of the tire equator line CL
It is preferable to provide 2.5%, preferably symmetrically.

If the thickness Tc of the separation rubber layer 9 does not exceed 0.3 mm than the thickness Th of the rubber portion 10, the effect of improving the belt durability is small. Conversely, if the thickness Tc exceeds 1.5mm, the belt durability increases. The sex worsens.

In the present invention, a conventionally known metal cord can be used as the metal cord of the belt layer 7, and for example, a steel cord can be preferably used. Carcass layer 4
As the reinforcing cord, an organic fiber cord can be used, and for example, a polyester cord can be preferably used.

A preferred example of the organic fiber cord of the belt edge reinforcing layer 8 is a nylon cord. This belt edge reinforcing layer 8 is, in the above embodiment,
Although an example in which two layers are provided is shown, the present invention is applicable to a pneumatic radial tire having no belt edge reinforcing layer 8.
It can be suitably used. Preferably, at least one belt edge reinforcing layer 8 is disposed on each of the outer peripheral sides of both ends of the belt layer.

The rubber constituting the separation rubber layer 9 is not particularly limited as long as the belt layer 7 can be separated from the carcass layer 4 within the above-mentioned thickness range, but preferably has a 100% modulus of 3%. It is preferred to use a rubber of ~ 8 MPa.

The present invention particularly relates to JATMA (JATMA YEAR BO
OK 1997) can be preferably used for pneumatic radial tires for small trucks having an aspect ratio of 0.85 or less, but is not limited thereto. Similarly, an aspect ratio defined by JATMA of 0.85 or less can be used. A pneumatic radial tire for a passenger car may be used. As the lower limit of the aspect ratio,
Any value may be used as long as it can be used as a flat pneumatic radial tire, and 0.50 can be exemplified from the viewpoint of a tire currently used.

[0017]

[Example] The tire size was 205 / 60R17.5 1
11 / 112L, the tires 1 to 5 of the present invention, the comparative tires 1 to 4, and the separation rubber, in which the width W and the thickness Tc of the separation rubber layer were changed as shown in Table 1 in the tire having the configuration shown in FIG. A conventional tire having no layer was produced.

Each of these test tires was rim size 17.5.
It was mounted on a rim of × 6.00 and subjected to an evaluation test for belt durability and rudder wander rig property under the following measurement conditions. The results shown in Table 1 were obtained.

Belt durability Each test tire was mounted on a drum tester and the air pressure was 600 kP.
a, Drum diameter 1707mm under the condition of load 10.69kN
The distance traveled until a tire failure occurred on the drum was measured, and the result was evaluated using an index value with the conventional tire being 100. The greater this value, the better the belt durability.

Rudder wandering property Each test tire was set to an air pressure of 600 kPa, mounted on a small truck of 3 tons, and a feeling test was performed by a test driver on a rutted road. The evaluation was based on a perfect score. The larger this value is, the better the rut wandering property is.

[0021]

[Table 1]

As is clear from Table 1, it can be seen that the tire of the present invention can greatly improve the belt durability and the rut wander rig property. In addition, each test tire was mounted on a small truck in the same manner as above, and a feeling test of steering stability was performed by a test driver on a test course, and it was at the same level as the conventional tire, and high steering stability was achieved. Confirmed that it can be secured.

[0023]

As described above, the present invention relates to a pneumatic radial tire having an aspect ratio of 0.85 or less provided with two belt layers in which metal cords are arranged, and a tread center area between a carcass layer and a belt layer. By specifying and arranging a separation rubber layer for separating the belt layer from the carcass layer within the above range, the tread rigidity on the shoulder side can be reduced, thereby improving belt durability and rut wandering. And the bending rigidity of the entire tread can be kept high, so that the high steering stability which is an advantage of the flat tire is not impaired.

[Brief description of the drawings]

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

FIG. 2 is an enlarged sectional view of a main part of FIG.

[Explanation of symbols]

Reference Signs List 1 tread portion 2 side wall portion 3 bead portion 4, 4A, 4B carcass layer 5 bead core 6 bead filler 7, 7A, 7B belt layer 7a belt layer end 8 belt edge reinforcing layer 9 interlayer rubber layer f metal cord

Continued on the front page (51) Int.Cl. ⁶ Identification code FI B60C 11/00 B60C 11/00 F 15/00 15/00 G

Claims (4)

[Claims] 1. An aspect ratio of 0.85 in which two belt layers in which metal cords are arranged are provided on a carcass layer outer peripheral side of a tread portion.
In the following pneumatic radial tire, a separation rubber layer for separating the belt layer from the carcass layer is arranged in a tread center region between the carcass layer and the belt layer at a width of 20 to 45% of a maximum belt width Wb, And its thickness Tc
At the midpoint position P between the tire equator line CL and the end of the belt layer having the maximum belt width Wb is 0.3 to 1 thicker than the thickness Th of the rubber portion between the reinforcing cord of the carcass layer and the metal cord of the belt layer. A pneumatic radial tire with a thickness of 5 mm. 2. At least one belt edge reinforcing layer is disposed on each of outer peripheral sides of both ends of the belt layer.
The pneumatic radial tire according to 1. 3. The pneumatic radial tire according to claim 1, wherein the separation rubber layer is made of a rubber having a 100% modulus of 3 to 8 MPa. 4. The pneumatic radial tire according to claim 1, 2, or 3, wherein the pneumatic radial tire is for a small truck.