JPH07205609A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To increase side rigidity and achieve a light tire, by forming carcass chords of tires from organic fiber and putting a plurality of primary twisted threads in order after unprocessed fiber has been primary twisted, and using specified and mutually reversely twisted threads in which the primary twisting and the reverse final twisting are applied. CONSTITUTION:The carcass chords of tires are formed from organic fiber and after the organic unprocessed threads have been primary twisted to obtain a primary twisting coefficient N1 stipulated in the following formula, a plurality of primary twisted threads are put in order and mutually reversely twisted threads subjected to find twisting, reverse twisting against the primary threads, to get a final twisting coefficient N2 stipulated in the following formula are used. In this case, the mutually reversely twisted threads are used so that N1, N2 are satisfied in the formula; (D2/D1)<1/2N2/N1<=8, N2<0.68 N1=n1(0.139D1rho)<1/2>X10<-3>, N2=n2(0.139D2rho)<1/2>X10<-3>, where the preparatoty twisted number n1 (times/10cm), the chief twisted number n2 (times/10cm), indication denier of preparatory twisted flux D1, total indication denier D2, S.G of organic fiber rho(g/cm<3>).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a pneumatic tire in which a twisted yarn of organic fiber is used for a carcass cord, in which the tire side irregularities are reduced (the irregularity index is increased), the cord initial tensile rigidity is increased, and the side tension is increased. The present invention relates to a pneumatic tire having improved rigidity and reduced tire weight.

[0002]

2. Description of the Related Art Conventionally, when an organic resin fiber such as polyester is used for a carcass cord of a tire, the number of lower twists n ₁ and the number of upper twists n ₂ are set for the purpose of not reducing the fatigue resistance of the cord. Only equal (n ₁ = n ₂ ) twisted structure cords have been used.

Usually, the upper twist coefficient N ₂ has a value of about 0.7, and the lower twist coefficient N ₁ has a value of about 0.5, which is used when the number of upper twists and the number of lower twists are considerably large. I've been. For example, in the case of 1500 D / 2 fiber, the lower twist number is about 40 times / 10 cm, and the upper twist number is about 40 times / 10 cm, 1
In the case of 000D / 2 fiber, the number of undertwist is about 50 times / 10c
m, the number of twists about 50 times / 10 cm has been adopted.

For the purpose of not reducing the fatigue resistance of the cord, a cord having a high twist structure has been used with the number of lower twists n ₁ and the number of upper twists n ₂ being equal. Therefore, the twisting cord initial tensile rigidity is suppressed, side unevenness is reduced (the unevenness index is increased), and the side rigidity is increased. It was also disadvantageous when the tire diameter was reduced by increasing the diameter and lowering the cord coating rubber gauge.

From the above, the fatigue resistance is not lowered while the polyester fiber is used, and
To achieve both of (a) reducing side irregularities (increasing the irregularity index), (b) enhancing side rigidity, and (c) reducing the cord diameter to achieve tire weight reduction. , It is difficult in a balanced twist structure of n ₁ = n _{2 in which} the number of lower twists n ₁ is equal to the number of upper twists n ₂ .

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to change the number of upper twists and the number of lower twists of a double twist yarn used for a carcass cord of a pneumatic tire to reduce tire side unevenness (the unevenness index is large). ), It is to provide a pneumatic tire that enhances the initial tensile rigidity of the cord, enhances the side rigidity, and achieves tire weight reduction.

[0007]

The present inventor has found that the number of lower twists n
Make the number of twists n ₂ equal to or less than ₁

[Equation 2] If the twisting coefficient N ₂ related to the twisting angle is equal to or greater than 0.68, the cord diameter increases, the initial tensile rigidity of the cord decreases, and the heat shrinkage rate of the cord increases. Since it is in the direction of doing so, the side unevenness is large (the unevenness index becomes small), the side rigidity is reduced, and it is found that there is a disadvantage in that the tire cannot be made lighter,

Also in the case of N ₂ / N ₁ > 8, the cord diameter tends to increase, the initial tensile rigidity and strength of the cord tend to decrease, the side unevenness increases (the unevenness index decreases), and the side rigidity also increases. We found that there is a demerit in that it decreases, and it becomes impossible to reduce the weight of the tire, and from these viewpoints,

[Equation 3] Then, the present inventors have reached the present invention by finding that the above object can be achieved.

That is, the present invention is as follows. (1) The carcass cord of the tire is made of organic fiber, and the organic fiber raw yarn is _first twisted to have a lower twist coefficient N ₁ defined by the following formula, and then a plurality of the lower twist yarns are gathered together. In a tire using a double-twisted yarn that is twisted in the opposite direction to the lower twist and has an upper twist coefficient N ₂ defined by the following formula, the N ₁ and N ₂ are:

[Equation 4] However, the lower twist number n ₁ (times / 10 cm) and the upper twist number n ₂ (times / 10
cm) When the denier D ₁ of the ply-twisted yarn bundle, the total denier D ₂ and the specific gravity ρ (g / cm ³ ) of the organic fiber are given, N ₁ = n ₁ × (0.139 × D ₁ / ρ) ^1/2 × A pneumatic tire having a carcass cord using twin-twisted yarn of 10 ⁻³ N ₂ = n ₂ × (0.139 × D ₂ / ρ) ^1/2 × 10 ⁻³ .

(2) The fiber type used for the carcass cord is one type of fiber selected from the group consisting of polyester fiber, polyamide resin fiber, and rayon fiber (1)
Pneumatic tire described.

In the present invention, the number of lower twists n ₁ (turns / 10 cm) and the number of upper twists n ₂ (turns / 10 cm), the lower twist coefficient N ₁ and the upper twist coefficient N
_{If 2} , then n ₂ > n ₁ , N ₂ ≦ 8N ₁ and N ₂ <0.68
Therefore, in the case of so-called ordinary twist in which the direction of the lower twist and the direction of the upper twist are opposite to each other in the twisted cord structure as in the present invention, either the normal Z twist or the S twist,
It is usual that the direction of the ply-twisted yarn bundle is parallel to the direction of the strand after ply-twisting, but in the case of the present invention, the ply-twisted yarn bundle is twisted in the ply-twisted direction The helix radius forming is smaller and the voids between filaments are smaller. That is, the cord diameter is reduced, and therefore, when the coating rubber gauges above and below the cord are made the same as those of the conventional one, the rubber volume can be reduced, and the tire can be made lighter.

In the cord of the present invention, the voids between the filaments are reduced, and the radius of the twisted helix is reduced. Therefore, the cord diameter is reduced, and when the cord is pulled, a twisted structure that easily exhibits the tensile rigidity of the filament itself is obtained. Since the initial tensile rigidity of the cord is improved, the side unevenness index of the tire is increased (as defined below, the conventional example is in the numerator, and the side unevenness index increases as the side unevenness decreases). The side rigidity can be increased.

The definition of the fatigue index used in the examples of the present invention will be described because it also serves to explain the terms used in the present invention. In GY type tube fatigue test in JIS standard {rotation speed of cord to be measured / rotation speed of conventional cord} ×
Let 100 be the fatigue index. The larger the value, the better.

The side unevenness index is a maximum width average value of four points on the tire circumference at the normal internal pressure (JIS or JATMA) of the conventional example (control) tire, W ₁ , and the circumference on the circumference of the carcass cord joint overlap portion. min. The maximum tire width is W ₂ . When the tires to be measured are w ₁ and w ₂ , respectively, (W ₁ −W ₂ ) / (w ₁ −w ₂ ) × 100 is taken as the side unevenness index. Since the measured value of the control tire is in the numerator, the smaller the side unevenness of the measured tire,
The side unevenness index becomes large.

The tire weight reduction rate index is measured by changing the cord diameter so that the cord upper and lower rubber gauges of the treat are the same as those of the conventional one when the gauge of the coating rubber is changed. When the same
When the treat weight of the conventional example (control) is W and the treat weight to be measured is w when the treat area is constant, W / w × 100 is a tire weight reduction index. Since the weight of the control treat is also in the numerator, the smaller the weight w of the measured treat, the larger the tire weight reduction index.

[0016]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. (1) Examples 1 to 3 and Comparative Examples 1 to 4 For the tire size 155 / 70R12, polyester fiber was used as the carcass cord fiber type, and 1000
The denier twin twist yarn (1000D / 2) has a twist structure,
Initial twist rigidity index of the cord (JIS standard when the number of lower twist n ₁ , the number of upper twist n ₂ , the lower twist coefficient N ₁ , the lower twist coefficient N ₂ and the cord diameter (mm) are set to the values shown in Table 1. Chord initial modulus), chord strength index, fatigue index (JIS standard G
Y tube test), side irregularity index, and tire weight reduction index were measured. The results are shown in Table 1.

[0017]

[Table 1]

(2) Examples 4 to 6 and Comparative Examples 5 to 8 For the tire size 185 / 70R14, polyester fiber was used as the carcass cord fiber type, and 1500
The denier twin twist yarn (1500D / 2) has a twist structure,
The same characteristic values as in Example 1 were measured when the number of lower twists n ₁ , the number of upper twists n ₂ , the lower twist coefficient N ₁ , the upper twist coefficient N ₂ , and the cord diameter (mm) were set to the values shown in Table 2. did. The results are shown in Table 2.

[0019]

[Table 2]

(3) Example 7, Comparative Example 9 For tire size 155 / 70R12, polyamide resin fiber (trademark nylon 66) was used as the carcass cord fiber type and 1260D / 2 had a twisted structure, and the same as Example 1. Further, the same characteristic values as in Example 1 were measured when n ₁ , n ₂ , N ₁ , N ₂ and the cord diameter (mm) were set to the values shown in Table 3. The results are shown in Table 3.

[0021]

[Table 3]

(4) Examples 8 and 9 and Comparative Example 10 For tire size 185 / 70R14, polyamide resin fiber (trademark nylon 66) and rayon were used as the carcass cord fiber species, and 1890D / 2 and 1 respectively.
When 650D / 2 has a twisted structure and n ₁ , n ₂ , N ₁ , N ₂ and the cord diameter (mm) are set to the values shown in Table 4 as in Example 1, the same as in Example 1 is obtained. The characteristic value was measured. The results are shown in Table 4.

[0023]

[Table 4]

[0024]

INDUSTRIAL APPLICABILITY The unbalanced twisted structure cord having a reduced number of lower twists of the present invention reduces unevenness on the tire side (increased the unevenness index), enhances the initial tensile rigidity of the cord, and enhances the side rigidity, Achieve weight reduction of tires.
Further, the total number of twists of the number of lower twists + the number of upper twists is reduced as compared with the conventional balanced twist structure cord in which the number of lower twists and the number of upper twists are equal to each other, resulting in cost reduction in the twisting process.

Claims (2)

[Claims] 1. A carcass cord of a tire is made of an organic fiber, and the fiber twist has a lower twist coefficient N ₁ defined by the following formula.
After twisting the lower twist so as to obtain, a plurality of the lower twisted yarns are gathered to obtain a double twisted yarn in which the upper twist is N _{2 in the} direction opposite to the lower twist and defined by the following formula. In the tire used, the N ₁ and N ₂ are as follows: However, the lower twist number n ₁ (times / 10 cm) and the upper twist number n ₂ (times / 10
cm) Under-twisted yarn bundle display denier D ₁ , total display denier D ₂ , and organic fiber specific gravity ρ (g / cm ³ ), N ₁ = n ₁ × (0.139 × D ₁ / ρ) ^1/2 × A pneumatic tire having a carcass cord using twin-twisted yarn of 10 ⁻³ N ₂ = n ₂ × (0.139 × D ₂ / ρ) ^1/2 × 10 ⁻³ . 2. The pneumatic tire according to claim 1, wherein the fiber type used for the carcass cord is one type of fiber selected from the group consisting of polyester fiber, polyamide resin fiber, and rayon fiber.