JPH11165503A - Radial tire for small truck - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure excellent stability in operation and rut wondering resistance without deteriorating durability. SOLUTION: In a radial tire for small trucks, in which two belt layers 7A and 7B are provided and whose compression rate is 0.8 or less, the in-plane flexural rigidity of each of the belt layers 7A and 7B is made 2200 kgf.mm<2> or more, and the out-plane flexural rigidity of a steel cord (f) each of the belt layers 7A and 7B is made 140 kgf.mm<2> or less, and the arrangement interval (a) of steel cords (f) is made 0.3 mm or more. The loss tangent tan σ20 and dynamic storage elasticity modulus of rubber constituting a tread section 1 at a temperature of 20 degree are set in the respectively ranges of 0.12<=tan σ20 <=0.20 and 4.2<=E'20 <=6.5.

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 used for a small truck, and more particularly, to a pneumatic radial tire having a flatness ratio of 0.85 or less in which two belt layers are arranged. The present invention relates to a radial tire for a small truck capable of obtaining good steering stability and rut wandering resistance without causing a problem.

[0002]

2. Description of the Related Art In general, a radial tire for a light truck has good steering stability by arranging three belt layers in which steel cords are arranged on an outer peripheral side of a carcass layer in a tread portion to secure high cornering power. To demonstrate. By the way, in recent years, flat tires have also been developed for radial tires for light trucks. However, such radial tires having three belt layers arranged to increase the rigidity of the tread portion have been developed by flattening. The rut wandering resistance deteriorates. In particular, a radial tire for a small truck having an aspect ratio of 0.85 or less has a problem that the wandering resistance is significantly reduced.

Therefore, conventionally, as a countermeasure, the belt layer has a two-layer structure to reduce the rigidity of the tread portion and improve the resistance to rudder wandering, while the rubber constituting the tread portion has high grip performance. There has been proposed a technique in which a cornering power is increased by using a rubber capable of exhibiting excellent steering stability. However, when such a rubber is used for the tread portion, there is a problem that heat resistance is reduced and durability is deteriorated.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a radial tire for a small truck capable of ensuring good handling stability and rut wandering resistance without causing a problem of durability. It is in.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a radial light truck for flat trucks having an aspect ratio of 0.85 or less, in which two belt layers in which steel cords are arranged are provided on the outer peripheral side of a carcass layer of a tread portion. In the tire, the in-plane bending stiffness defined by the following equation for each belt layer is 2200 kgf · mm.
² or more, the out-of-plane bending stiffness per steel cord is set to 140 kgf · mm ² or less, the interval between the steel cords is set to 0.3 mm or more, and the rubber constituting the tread portion at 20 ° C. The loss tangent tan δ ₂₀ and the dynamic storage modulus E ′ ₂₀ are respectively 0.12 ≦ tan δ ₂₀ ≦
Characterized in that the _{^{0.20,4.2kgf / mm 2 ≦ E '2}} 0 ≦ 6.5kgf / mm 2.

In-plane bending stiffness = (Bending stiffness in the belt layer in-plane direction per steel cord) × (Number of steel cords per 50 mm in the belt layer tire width direction) Thus, the in-plane bending stiffness of both belt layers is increased. By setting, it is possible to exert a large cornering power by stepping on the belt layer at the time of cornering, so that good steering stability can be obtained. On the other hand, by setting the out-of-plane bending stiffness per steel cord of the belt layer in a low range, the belt layer can be deformed corresponding to the rut, so that good rut wandering resistance can be secured. it can.

Further, by specifying the physical properties of the rubber constituting the dread portion within the above range, it is possible to prevent the heat resistance from deteriorating and to reduce the steering stability due to the tread rubber being too soft. Absent.

[0008]

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 radial tire for a small truck 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,
3 is a bead part, CL is a tire center line. Inside the tire, two carcass layers 4 between the left and right bead portions 3
A, 4B are mounted, and both ends 4 of the inner carcass layer 4A
a is folded back from the inside of the tire to the outside so as to sandwich the bead filler 6 around the bead core 5. Both ends 4b of the outer carcass layer 4B are
A is configured to extend to the vicinity of the bead core 5 along the folded both ends 4a of A.

On the outer peripheral side of the carcass layer of the tread portion 1, two belt layers 7A and 7B in which steel cords f are arranged are provided. The two carcass layers 7A and 7B are arranged so that the steel cords f intersect each other with the inclination in the tire circumferential direction being opposite between the layers, and the inclination angle with respect to the tire circumferential direction is 16 ° to 26 °. Two edge cover layers 8 in which organic fiber cords such as nylon are wound in the tire circumferential direction are provided on the outer peripheral sides of both ends of the belt layers 7A and 7B.

Each of the belt layers 7A and 7B has an in-plane bending stiffness, which is the stiffness when the belt layer is bent in the in-plane direction (the direction in which the surface extends), is 2200 kgf · mm ² or more. However, this in-plane bending rigidity is defined by the following equation. In-plane bending stiffness = (Bending stiffness in the belt layer in-plane direction per steel cord) x (belt layer tire width direction 50 mm)
(The number of steel cords per unit) Further, each of the arranged steel cords f has an out-of-plane bending rigidity, which is a rigidity when bent in a direction intersecting with the belt layer, is set to 140 kgf · mm ² or less per one. An arrangement interval a, which is an interval between adjacent steel cords f, is set to 0.3 mm or more.

Further, a rubber portion 1A constituting the tread portion 1
The loss tangent tan δ ₂₀ at 20 ° C. and the dynamic storage modulus E ′ ₂₀ of the rubber at 0.1 ° C. are respectively 0.12 ≦ tan δ ₂₀ ≦ 0.2.
0, 4.2 kgf / mm ² ≦ E ′ ₂₀ ≦ 6.5 kgf / mm ² . In the radial tire for small trucks having the flatness ratio of 0.85 or less provided with the two belt layers 7A and 7B as described above, the in-plane bending stiffness of both belt layers 7A and 7B is set to be high as described above. Higher cornering power can be exerted by cornering when cornering, so good steering stability can be ensured, but the out-of-plane bending stiffness per steel cord should be set as described above. Thus, when the belt layer enters the rut, the belt layer is easily deformed correspondingly, so that the rut wandering resistance can be improved.

Also, a rubber portion 1A constituting the dread portion 1
By setting the loss tangent tan δ _{20 at} 20 ° C. and the dynamic storage elastic modulus E ′ ₂₀ of the rubber physical properties in the above ranges, heat generation can be suppressed to a low level, and steering stability due to a decrease in rigidity of the tread portion. There is no loss of sex. If the in-plane bending stiffness of each belt layer is smaller than 2200 kgf · mm ² , it is difficult to obtain good steering stability because the belt stiffness is insufficient. The upper limit of the in-plane bending stiffness is preferably set to 7500 kgf · mm ² because the uneven wear property deteriorates. It is preferable that both belt layers 7A and 7B are arranged with substantially the same in-plane bending rigidity.

If the out-of-plane bending stiffness exceeds 140 kgf · mm ² , it becomes difficult for the belt layer to follow and deform due to rut wandering. The lower limit of the out-of-plane bending stiffness can be set to 30 kgf · mm ² because the rolling resistance deteriorates. When the arrangement interval a of the steel cords f is less than 0.3 mm,
Since the peeling easily occurs between the steel cord f and the rubber, the durability of the belt decreases. The upper limit of the arrangement interval a is 1 mm because the scratch resistance (puncture, etc.) is deteriorated.
It is preferred that

Even if the loss tangent tan δ ₂₀ is less than 0.12 or the dynamic storage modulus E ′ ₂₀ is less than 4.2 kgf / mm ² , the steering stability is deteriorated, and Tangent tan δ
_{Even if 20} exceeds 0.20, the dynamic storage modulus E ′ ₂₀ is 6.
Even if it is larger than 5 kgf / mm ² , a problem of heat generation occurs, which causes a decrease in tread durability. In the present invention, the steel cord f of the belt layers 7A and 7B is a wire f
The flat cord shown in FIG. 2 where 1 is arranged in a flat shape can be preferably used. By adopting this flat code,
A belt layer having the above-described high in-plane bending rigidity and low out-of-plane bending rigidity can be easily obtained.

The radial tire for a small truck in the present invention is defined as JATMA (JATMA YEAR BOOK 1997).
The radial ply tire for a light truck specified in the above.

[0016]

[Example] The tire size was 205 / 60R17.5 1
In the tire having the configuration shown in FIG. 1, the in-plane bending stiffness of each belt layer, the out-of-plane bending stiffness per steel cord, the arrangement interval of the steel cords, the rubber of the tread portion, Tires 1 to 5 of the present invention, comparative tires 1 to 5, and conventional tires having loss tangent tan δ ₂₀ and dynamic storage modulus E ′ ₂₀ at 20 ° C., respectively, as shown in Table 1, were produced.

Each of these test tires was rim size 17.5.
It was mounted on a rim of × 6.00 and subjected to evaluation tests for wandering resistance, steering stability, and tread durability under the following measurement conditions. The results shown in Table 1 were obtained. Rutting resistance and steering stability Set the tire pressure to 600kPa and set it on a 2t light truck, conducted a feeling test with a test driver on a rutted road test course, and evaluated the results on a scale of 10 out of 10. did. With six or more points, it can be said that the rut wandering resistance and the steering stability are good. Tread durability Each test tire was mounted on a drum tester, and the air pressure was 600
kPa, load 10.69 kN, speed 120 km / h,
The distance when the tire was run on a drum having a drum diameter of 1707 mm until the tire was broken was measured, and the result was evaluated as an index value with the conventional tire being 100. The larger this value, the better the tread durability. If it is 130 or more, there is no problem.

[0018]

[Table 1]

As is clear from Table 1, all of the tires of the present invention have rut wandering resistance and steering stability exceeding 6 points, tread durability is more than 130, and good rut wandering resistance. It can be seen that the steering stability can be ensured and that there is no durable problem.

[0020]

As described above, according to the present invention, the belt layer has two layers.
In the radial tire for light trucks having an aspect ratio of 0.85 or less, the in-plane bending stiffness of each belt layer and the out-of-plane bending stiffness per steel cord are specified as described above, and the rubber of the dread portion is provided. By setting the physical properties in the above-described range, good steering stability and rut wandering resistance can be obtained without causing a problem of tread durability.

[Brief description of the drawings]

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

FIG. 2 is an enlarged sectional view showing a preferred example of a steel cord of a belt layer.

[Explanation of symbols]

Reference Signs List 1 tread portion 1A rubber portion 2 sidewall portion 3 bead portion 4A, 4B carcass layer 5 bead core 6 bead filler 7A, 7B belt layer 8 edge cover layer f steel cord

Claims (2)

[Claims] 1. An aspect ratio of 0.1 in which two belt layers in which steel cords are arranged are provided on an outer peripheral side of a carcass layer of a tread portion.
For radial tires for light trucks of 85 or less, the in-plane bending stiffness defined by the following equation for each belt layer is 220
0 kgf · mm ² or more, the out-of-plane bending stiffness per steel cord is 140 kgf · mm ² or less, the arrangement interval of the steel cords is 0.3 mm or more, and rubber constituting the tread portion is used. Loss tangent at 20 ° C
The tan δ ₂₀ and the dynamic storage modulus E ′ ₂₀ are each 0.12 ≦
tan δ ₂₀ ≦ 0.20, 4.2 kgf / mm ² ≦ E ′ ₂₀ ≦ 6.5
kgf / mm ² radial tire for small trucks. In-plane bending stiffness = (Bending stiffness in the belt layer in-plane direction per steel cord) x (belt layer tire width direction 50 mm)
Per steel cord) 2. The radial tire for a light truck according to claim 1, wherein the steel cord is a flat cord.