JPH08150809A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE: To make improvements in the vibro-riding comfort and maneuvering stability of a pneumatic radial tire by using an organic fiber cord as a belt layer of this tire. CONSTITUTION: In this pneumatic tire, at least one layer out of tire belt layers made up of more than two sheets mingled has applied a primary twist serving as a primary twist factor N1 to be prescribed with the following equation, and then, it uses double twisted yarn applied with a final twist serving as a final twist factor N2 to be prescribed at the following equation in the reverse direction of the primary twist after paralleling plural pieces of the primary twist. Thus it uses the double twisted yarn being so constituted that when N1 and N2 are 1<N2 /N1 <=5 and N2 <0.30, where, a primary twist number n1 (time/10cm), a final twist number n2 (time/10cm), display denier number D1 of a primary twist yarn bundle, total display denier D2 fiber of specific gravity ρ(g/cm<3> ) are set like that, it becomes N1 =n1 ×(0.139×D1 /ρ)<1/2> ×10<-3> . N2 =n2 ×(0.139×D2 /ρ)<1/2> ×10<-3> .

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 using an organic fiber cord as a cord used in a belt layer.

[0002]

2. Description of the Related Art Conventionally, as a belt portion of a pneumatic radial tire for a passenger car, a rubber steel cord having a predetermined angle with respect to the equatorial direction of the tire and mainly provided with a steel cord. A pneumatic radial tire is known in which at least two belts made of a composite are laminated to improve steering performance, wear resistance performance, and the like that match vehicle performance.

In addition to the above, one steel cord / rubber composite body and one organic fiber / rubber composite body are combined into two.
There was a single sheet structure or a double sheet structure of organic fiber / rubber composite.

In these organic fiber cords, the number of lower twists n ₁ and the number of upper twists n _{2 of} mainly nylon fibers are equal (n ₁ = n _2).
) A twisted structure cord was used.

[0005]

Particularly, the tire using the two-fiber structure of the organic fiber / rubber composite for the belt portion ensures a sufficient vibration riding comfort when traveling on an unpaved rough road with a heavy load. On top of that, maneuvering stability was also required.

[0006] However, if the twist structure in which the number of lower twists n ₁ and the number of upper twists n ₂ are equal (n ₁ = n ₂ ), that is, the balanced twist structure, it is difficult to achieve both of these contradictory physical properties. However, the driving stability was insufficient because the emphasis was placed on vibration ride comfort.

An object of the present invention is to solve the problems of the conventional pneumatic radial tire as described above, and to maintain the vibration riding comfort and the steering stability without impairing other performances. To provide.

[0008]

In order to solve the above-mentioned problems, the present inventor has found that at least one of the belt layers of a tire formed by interlacing two or more sheets has a lower twist coefficient N defined by the following formula. After the undertwisting of ₁ is applied, a plurality of the undertwisted yarns are gathered together and the twisted twine yarn having the above-mentioned twisting factor N _{2 in the} opposite direction to the undertwisting is used. N ₁ and N ₂ are 1 <N ₂ / N ₁ ≦ 5 and N ₂ <0.30 However, the number of lower twists n ₁ (turns / 10 cm), the number of upper twists n ₂ (turns 10 cm) N ₁ = n ₁ × (0.139 × D ₁ / ρ) ^1/2 × 10 ^-3 N _{2 where} D _{1 is} the display denier and D _{2 is} the total specific gravity of the display denier ρ (g / cm ³ ). = N ₂ × (0.139 × D ₂ / ρ) ^1/2 × 10 ⁻³ by using the twin-twisted yarn in the belt layer of the pneumatic tire,

The fibers used for the belt layer cord are nylon fibers, polyester fibers, rayon fibers,
By using an organic fiber cord made of polyamide fiber for the belt layer, the vibration riding comfort and steering stability of the pneumatic tire are improved.

[0010]

[Function] According to the present invention, the lower twist number n ₁ (turns / 10 cm), the upper twist number n ₂ (turns / 10 cm), the lower twist coefficient N ₁ and the upper twist coefficient N ₂
Since n ₂ > n ₁ and especially 1 <N ₂ / N ₁ ≦ 5, in the twisted cord structure, the direction of the lower twist and the direction of the upper twist are opposite to each other as in the present invention. In the case of so-called ordinary twist, which is usually Z twist or S twist, the direction of the lower twisted yarn bundle is usually parallel to the direction of the strand after the upper twist, but in the case of the present invention, the lower twisted yarn Since the bundle is twisted in the direction of the upper twist, the radius of the helix for making the upper twist of the lower twisted yarn bundle becomes smaller, and the converging force of the filament is increased.

Here, since the filament converging force is increased, tension is easily applied to the filament itself when the cord is pulled, and tensile rigidity is easily exhibited. In addition, N ₂ <0.30 The filament has a shape close to a straight with less twisting, the rigidity in the longitudinal direction of the cord is increased, and the steering stability is improved.

Further, when the spiral radius forming the upper twist of the lower twisted yarn bundle becomes smaller, the code diameter decreases, and when the coating rubber gauges above and below the cord are made the same, the rubber gauge can be reduced and the tire can be made lighter. .

In addition, in such an organic fiber cord having a small number of twists, the total twist number of the number of upper twists and the number of lower twists is smaller than that of the conventional cord, so that the productivity in the twisting process is improved. Is improved.

Here, N ₂ / N ₁ ≦ 1 or N ₂
When / N ₁ > 5, the initial tensile rigidity of the organic fiber cord is lowered, and sufficient steering stability cannot be obtained.

Also, when N ₂ ≧ 0.30, the same problem as described above occurs and sufficient steering stability cannot be obtained.

[0016]

EXAMPLES Examples of the present invention will be described below.
The invention is in no way limited by this example. (1) Table 1 The tire size is 165 / SR13 structure, a specific organic fiber is used as the belt layer, and the number of lower twists n ₁ and the number of upper twists n
₂ , when the lower twist coefficient N ₁ and the upper twist coefficient N ₂ were set to the values shown in Table 1, the tensile rigidity index (JIS standard code initial modulus) and steering stability of the cord were measured by the following methods. . Initial tensile stiffness index of the cord When the cord was stretch-broken using an ordinary tensile breaking tester according to JIS standard, 0.33 gf / D and 0.66
When the elongations corresponding to the tensions T ₁ and T ₂ (kgf) at gf / D are L ₁ and L ₂ (%), E = (T ₂ −T ₁ ) / (L ₂ −L ₁ ) × 100 It is defined as the initial tensile rigidity of the cord. When the cord initial tensile rigidity of the conventional example is E ₁ and the cord initial tensile rigidity to be compared is E, the cord initial tensile rigidity index was obtained from E / E ₁ × 100. Steering stability index 1.70kg / cm internal pressure on a drum with an outer diameter of 3000mm
Install the test tire adjusted to ² , load the load specified in JATMA, then preliminarily run at a speed of 30 km / hour, readjust the internal pressure to 1.70 kg / cm ² under no load, The load for preliminary running was applied again, and positive and negative continuous slip angles were applied up to 14 ° on the drum at the same speed. The cornering force (CF) at each positive and negative speed is measured, and the following formula:

[Equation 1] The cornering power (CP value) was determined by. The index value was converted into the CP value of each test tire, and the control tire was set to 100. The larger this index, the better the maneuverability.

[0017]

[Table 1]

(2) Table 2 The tire size is 185 / 70R14 structure, a specific organic fiber is used as the belt layer, and the number of lower twists n ₁ and the number of upper twists n
_2. For the cords when the lower twisting coefficient N ₁ and the upper twisting coefficient N ₂ are set to the values shown in Table 2, the tensile rigidity index (JIS standard code initial modulus) and the steering stability index are set as in Table 1. Each was measured.

[0019]

[Table 2]

[0020]

According to the organic fiber cord of the present invention,
Improves the tensile rigidity of the cord, thereby improving the ride comfort and steering stability of the tire. In addition, the total number of twists of the number of upper twists + the number of lower twists is reduced compared to the conventional cord having a structure in which the number of lower twists and the number of upper twists are equal,
Productivity is improved in the twisting process.

[0021]

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a belt layer of a pneumatic radial tire.

Claims (2)

[Claims] 1. At least one of the belt layers of a tire formed by interlacing two or more layers is subjected to undertwisting with an undertwisting coefficient N ₁ defined by the following formula, and then a plurality of the undertwisted yarns are obtained. A twin-twisted yarn is used in which the ply-twisted yarns having the ply-twisting coefficient N ₂ defined by the following formula in the opposite direction to the ply-twisted yarn are applied and N ₁ and N ₂ are 1 <N ₂ / N ₁ ≦ 5. And N ₂ <0.30 However, the number of lower twists n ₁ (times / 10 cm), the number of upper twists n ₂ (times / 10 cm), the number of deniers D ₁ of the lower twisted yarn bundle, the total deniers D ₂ The specific gravity of the fiber ρ ( g / cm ³ ), N ₁ = n ₁ × (0.139 × D ₁ / ρ) ^1/2 × 10 ⁻³ N ₂ = n ₂ × (0.139 × D ₂ / ρ) ^{1 /} A pneumatic tire having a belt layer using a double twist yarn of ² × 10 ⁻³ . 2. The fiber used for the belt layer cord is
The pneumatic tire according to claim 1, comprising a nylon fiber, a polyester fiber, a rayon fiber, and a polyamide fiber.