JP2001063308A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent interface separation, and improve run-flat durability by setting a twist coefficient in a specified range by a specified formula I of a reinforcing fiber code buried in an outer ply, and setting a twist coefficient in a specified range by a specified formula II of a reinforcing fiber code buried in an inner ply. SOLUTION: In a carcass layer, a twist coefficient NT(0) of a fiber code of an outer ply is not less than 0.15 and less than 0.35, and the twist coefficient NT(0) is shown by a formula I (in the formula I, N1(0) shows an upper twist number (time/10 cm) of the fiber code, DTOTAL(0) shows a total decitex (dtex) number of the fiber code, ρ(0) shows a specific gravity of composing resin). A twist coefficient NT(1) of the fiber code of an inner ply is not less than 0.35 and less than 0.65, and the twist coefficient NT(1) is shown by a formula II (in the formula II, N1(1) shows an upper twist number (time/10 cm) of the fiber code, DTOAL(1) shows a total decitex (dtex) of the fiber code, ρ(1) shows a specific gravity of composing resin). It is thus possible to improve run-flat durability.

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 fiber cord for reinforcing a carcass layer (hereinafter referred to as a ply cord) in which a rubber reinforcing layer (side reinforcing layer) is disposed on a sidewall portion of the tire. Sometimes)
The present invention relates to an improved pneumatic radial tire using a cord having a specific twist coefficient.

[0002]

2. Description of the Related Art Conventionally, pneumatic safety tires are often used for running a considerable distance (so-called run flat running) even after the air pressure is lost due to a puncture or the like. Has been proposed.
Currently, pneumatic safety tires that are being developed are often side reinforced types. In the side reinforced type, a relatively hard reinforcing rubber layer having a crescent cross section is provided on the inner surface of the carcass layer on the sidewall, and one end of the rubber layer is provided at one end. Are overlapped with the belt layer across the carcass, and the other end is strengthened by being arranged to overlap with the bead filler. If the tire punctures during running and the air escapes, the load is supported by the inherent rigidity of the sidewall reinforced by the reinforcing rubber layer, and although the speed must be slightly reduced, the run-flat running for a predetermined distance It can be carried out.

However, in such a pneumatic tire, when an aliphatic polyamide fiber cord such as nylon 46 or nylon 66 is used as the ply cord, the dimensional stability of the tire is reduced due to low modulus and large creep. In addition, when the tire is left attached to the car for a long time, there is a drawback that a flat spot is generated and riding comfort is deteriorated. Recently, many attempts have been made to improve the performance of tires for passenger cars by using improved polyester fibers having a relatively high initial modulus, excellent dimensional stability and high strength for ply cords. However, also in this case, in running when the internal pressure of the tire is low (run-flat running), the sidewall portion of the tire is extremely deformed, and the internal temperature becomes extremely high due to self-heating inside the tire, so that the internal temperature becomes relatively high. Even with a polyester fiber cord having heat resistance, peeling occurred at the interface of the adhesive layer, and the durability in run flat running was still insufficient. On the other hand, in recent years, demands for safety have been increasing, and safety tires have been demanded even for general-purpose passenger car tires having an aspect ratio of 60% or more. There is also a demand for thinner tire sidewalls. Furthermore, it is naturally required to be able to perform run-flat driving and at the same time to perform in normal driving at the time of internal pressure charging.

[0004]

SUMMARY OF THE INVENTION Under such circumstances, the present invention has excellent flat spot resistance, and has excellent peelability at the interface of the adhesive layer of the ply cord during running, particularly during run flat running. In addition to suppressing deformation of the tire sidewall and rim disengagement, the tire heat generation temperature is suppressed,
It is an object of the present invention to provide a pneumatic tire having excellent tire durability.

[0005]

Means for Solving the Problems The present inventor has proposed such a method.
After extensive research to develop pneumatic tires,
Twist coefficient of outer ply cord of outermost layer
Is smaller than the twist coefficient of the inner ply cord.
Have achieved that purpose. The present invention
Has been completed based on such knowledge. Sand
The present invention relates to a radial ply reinforced with a fiber cord.
At least two carcass layers, wherein the radial
Outer ply disposed on the outermost layer in the tire radial direction of the ply
Twist coefficient NT of fiber cord for reinforcement embedded in rye_(O)
Is not less than 0.15 and less than 0.35,
For reinforcement buried in the inner ply arranged inside
Twist coefficient NT of fiber cord_(I)Is 0.35 or more and 0.65
Pneumatic radial tires characterized by the following
To provide. However, the above twist coefficient NT_(O), N
T_(I)Is the following formula NT_(O)= N_{1 (O)}× ｛0.1396 × (0.9 × D_{TOTAL (O)}/ 2ρ_(O))｝^1/2× 10^-3 ... (I) NT_(I)= N_{1 (I)}× ｛0.1396 × (0.9 × D_{TOTAL (I)}/ 2ρ_(I))｝^1/2× 10^-3 ... (II) (in the above formula, N_{1 (O)}And N_{1 (I)}Is the outer
Reinforcing fiber cord embedded in lie and inner ply
Indicates the number of twists (times / 10 cm). Also,
D_{TO TAL (O)}, D_{TOTAL (I)}Are the outer ply and
And reinforcing fiber cord embedded in the inner ply
Shows the taldecitex (dtex) number. ρ_(O)And ρ
_(I)For the outer ply and the inner ply respectively
Indicates the specific gravity of the resin that composes the embedded reinforcing fiber cord.
You. ).

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Pneumatic radial tire of the present invention
Is the radial ply cord that forms the carcass layer,
Primarily twisted with a yarn bundle consisting of organic fiber filaments
Bundles multiple twisted yarns and twists in the opposite direction to the twisted yarn.
The twisted twisted yarn is used, and the side wall part
This is especially true when a rubber reinforcing layer is
It is effective for And in the carcass layer, the outer
The fiber cord of the ply is a twist represented by the formula (I).
Coefficient NT_(O)Is not less than 0.15 and less than 0.35
In addition, the fiber cord of the inner ply is represented by the above formula (II).
Twist coefficient NT_{(I )}Is 0.35 or more and 0.65 or less
It is necessary that Furthermore, outer ply fiber
The cord has a twist coefficient of NT_(O)Is 0.20 to 0.30
It is particularly preferable that the range is 0.20 to 0.25.
Good. The inner ply fiber cord has a twist coefficient
NT_(I)Is preferably in the range of 0.41 to 0.60. here
The outer ply is the most tire in the carcass layer.
Refers to the radial ply located on the outside in the radial direction.
Located outside the neutral axis of the curvature of the dwall part
You. In addition, the inner ply is
One or more plies located radially inward of the tire
Say. At least one of these plies has a bead at each end.
Rolled up around the gear ring and fixed
I have. If the inner ply has multiple layers,
Coefficient NT of ply cord of inner ply_(I)
Is 0.35 or more and 0.65 or less.

In the present invention, since the reinforcing cord of the outer ply disposed outside the neutral axis of the curvature of the sidewall portion has a higher elastic modulus than the reinforcing cord of the inner ply disposed inside, By suppressing the deformation of the tire side wall during flat running and suppressing the self-heating of the tire, it is possible to suppress the decrease in adhesion to the cord, so the rim disengagement at the time of side force input to the tire during cornering is reduced. Significant improvement. Also, the twist coefficient NT of the outer ply fiber cord
_{When (O)} is in the above range, the cord diameter can be reduced, and even if the coating rubber gauges above and below the cord are the same as the conventional one, the rubber volume required for ply production can be reduced. Can be thin. As a result, it is possible to reduce the heat generated in the sidewall portion due to the run flat running.

Further, the outer ply fiber cord
Is the number of twists N₁(Times / 10cm) and the number of lower twists N_Two(Times
/ 10 cm)₁/ N_TwoIs 1.17 or more and 1.70
Or less, particularly preferably 1.25 or more and 1.55 or more.
The following is preferred. The reason is the number of twists N₁
And number of lower twists N_TwoSo-called balanced twisted cord
The thickness of the sidewall is thinner than when using
Heat generated by the side wall due to run flat running
This is because it can be further reduced. Also used for carcass layer
The material of the ply cord is not particularly limited.
And aliphatic polyamide fibers such as nylon 66,
Aromatic polyamides such as rosephenylene terephthalamide
Fiber, polyethylene terephthalate, etc.
Fiber, rayon fiber, CO unit and olefin in the molecule
Polyolefin ketone fiber having a bond with a unit
Of these, aromatic polyamide fibers and polyester fibers are preferred.
Polyester fiber, rayon fiber and polyolefin fiber
Ton fibers are used. Also, the pneumatic tire of the present invention
In the carcass cord, the twist coefficient NT_{(O )}And N
T_(I)Satisfies the above range,
And inner ply cords of the same or different materials
You can use any combination of codes,
In terms of fatigue, the outer ply cord is made of aromatic poly.
It is preferable to use a material other than amide fibers.

In the pneumatic tire of the present invention, it is preferable to use a rubber reinforcing layer on at least a portion from the sidewall portion to the shoulder portion in order to suppress deflection of the sidewall when air is released. There are no particular restrictions on the location of the reinforcing layer, such as the positional relationship with the carcass ply, whether it is located on a part of the sidewall part or on the whole, or whether its end can reach the shoulder part. The arrangement position can be appropriately selected according to the conditions. The shape is not particularly limited. Further, the rubber reinforcing layer may be composed of a substantially homogeneous rubber composition, or may be composed of a composite with particles, fibers and the like. For the rubber reinforcing layer, for example, a rubber having high hardness is usually used in order to exhibit a function of suppressing the compression deformation inside the sidewall. The rubber component of the rubber reinforcing layer is not particularly limited. For example, natural rubber (N
R), butadiene rubber (BR), styrene-butadiene rubber (SBR), isoprene rubber (IR) and the like. Among them, natural rubber and butadiene rubber are preferred from the viewpoint of the effect.

Next, the pneumatic tire according to the present invention will be further described with reference to the drawings. A pneumatic tire 1 which is an example of the present invention shown in FIG. 1 (right half cross-sectional view) has a bead ring 2 at both ends of a crown portion at a tip end in a tire radial direction.
Are laid in a row, and both ends of a radial ply reinforced with a fiber cord extending from one side of these side walls through the crown to the other side are axially outward around the bead ring. The carcass layer 4 is formed of a single inner ply 4a wound up and a single outer ply 4b outside the inner ply 4a. Then, a belt layer 5 and a tread portion 6 are sequentially arranged on the crown portion of the carcass layer.
Further, the rubber reinforcing layer 7 is provided so as to include at least a part from the sidewall portion to the shoulder portion. Here, the folded end of the inner ply 4a may be stopped near the upper part of the bead filler, but may be folded to both ends of the crown portion, for example, the structure as shown in FIG. The folded end of the outer ply 4b is
The bead ring may be folded from the outside to the inside, or a so-called down ply structure without winding up around the bead ring as shown in FIG.

[0011]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited by these. In addition, various measurements of the tire were performed by the following methods. (1) Run flat durability At room temperature of 38 (° C.) at an internal pressure of 3.0 (kgf / cm ² ),
After leaving for 4 hours, the valve core was removed and the internal pressure was reduced to 0 (kgf / c
m ² ), a load of 570 (kg) and a speed of 89 (km / km).
hrs) and a room temperature of 38 (° C.), a drum running test was performed. The running distance up to the occurrence of the failure at this time was defined as run flat durability, and the tire (control) of Comparative Example 1 was set at 1
The index was set to 00. The larger the index, the better the ranflat durability. (2) Normal running durability Under an internal pressure of 3.0 (kgf / cm ² ) at room temperature of 25 (° C.)
After standing for 4 hours, the internal pressure was readjusted to 3.0 (kgf / cm ² ), and the peripheral speed was set to 60 under a load twice the JATMA maximum load.
(Km / hrs) and pressed against the rotating drum to measure the running distance until a failure occurred. Tires for practical use were evaluated as (x) when they were 20,000 (km) or less, and as (○) when they exceeded 20,000 (km).

Examples 1 to 6 and Comparative Examples 1 to 3 A reinforcing rubber layer was provided inside the carcass layer of the side wall portion.
And the structure of the carcass ply is one inner ply
Roll both ends axially outward around the bead ring
Turn the end of the carcass up to the tread and
Both ends of one tarp ply axially around the bead ring
Fold inward to get a 225 / 60R16 radiator
Rutyre was prototyped by a conventional method. That is, in FIG.
And do not use the outer ply as the down ply,
1 except that it is folded back in the axial direction around the ring.
The tire structure was the same. Carcass layer of this prototype tire
Cord used for outer ply and inner ply
Table 1 shows the details of the carcass ply material.
Rayon cord, polyester cord (PET) and na
Twist coefficient NT using IRON 66 cord_{(O )}And N₁/ N
_TwoThe code which changed the value of was appropriately used. Like this
Run-flat durability and
And the normal running durability was measured by the method described above. result
Are shown in Table 1.

[0013]

[Table 1]

[0014]

[Table 2]

As shown in Table 1, the pneumatic tires of Examples 1 to 6 in which the cords having the specific twist coefficient according to the present invention are used for the cords of the outer ply and the inner ply have run-flat durability. It turns out that it is excellent. In particular the ratio of the upper twist N ₁ and the lower twist N ₂ (N
_{When 1} / N ₂ ) is 1.17 to 1.70, the run flat durability is excellent. In addition, the normal running durability at the time of filling the internal pressure was at a level without any problem for all tires.

[0016]

As described above, in the pneumatic radial tire of the present invention, the deformation of the side wall portion is suppressed during run flat running, and the interfacial peeling of the reinforcing cord of the carcass layer from the rubber adhesive layer is prevented. It has excellent run flat durability. Further, in the pneumatic tire of the present invention, since the internal heat generation of the tire can be suppressed by reducing the thickness of the sidewall portion, there is no problem even in normal running at the time of filling the internal pressure.

[Brief description of the drawings]

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

[Explanation of symbols]

 1: Pneumatic tire 2: Bead ring 3: Side wall part 4: Carcass layer 4a: Inner ply 4b: Outer ply 5: Belt layer 6: Tread part 7: Rubber reinforcing layer

Claims (7)

[Claims] 1. A radial ply reinforced with a fiber cord.
Having at least two carcass layers of
Outer layer located on the outermost layer in the radial direction of Luply
Twist coefficient NT of fiber cord for reinforcement embedded in ply
_(O)Is not less than 0.15 and less than 0.35,
Supplies buried in the inner ply placed inside the lie
Twist coefficient NT of heavy duty fiber cord_(I)Is 0.35 or more.
Pneumatic radial tie characterized by being 65 or less
Ya. However, the above twist coefficient NT_(O), NT_(I)Is the following formula NT_(O)= N_{1 (O)}× ｛0.1396 × (0.9 × D_{TOTAL (O)}/ 2ρ_(O))｝^1/2× 10^-3 ... (I) NT_(I)= N_{1 (I)}× ｛0.1396 × (0.9 × D_{TOTAL (I)}/ 2ρ_(I))｝^1/2× 10^-3 ... (II) (in the above formula, N_{1 (O)}And N_{1 (I)}Is the outer
Reinforcing fiber cord embedded in lie and inner ply
Indicates the number of twists (times / 10 cm). Also,
D_{TO TAL (O)}, D_{TOTAL (I)}Are the outer ply and
And reinforcing fiber cord embedded in the inner ply
Shows the taldecitex (dtex) number. ρ_(O)And ρ
_(I)For the outer ply and the inner ply respectively
Indicates the specific gravity of the resin that composes the embedded reinforcing fiber cord.
You. ). 2. A ratio N ₁ / N ₂ of the number of twists N ₁ (twice / 10 cm) and the number of twists N ₂ (twice / 10 cm) of the reinforcing fiber cord embedded in the outer ply is 1. The pneumatic radial tire according to claim 1, which is 17 or more and 1.70 or less. 3. The pneumatic radial tire according to claim 2, wherein N ₁ / N ₂ is 1.25 or more and 1.55 or less. 4. The pneumatic radial tire according to claim 1, wherein the reinforcing fiber cord embedded in the outer ply has a twist coefficient NT _{(O) of} not less than 0.2 and not more than 0.30. 5. The twisting coefficient NT _(I) of the reinforcing fiber cord embedded in the inner ply is 0.41 to 0.6.
The pneumatic radial tire according to claim 1, wherein the value is 0 or less. 6. The fiber cord according to claim 1, wherein the reinforcing fiber cord of the carcass layer is any organic fiber selected from aromatic polyamide fiber, polyolefin ketone fiber, polyester fiber and rayon fiber. Pneumatic radial tire. 7. The pneumatic radial tire according to claim 1, wherein the carcass layer comprises one outer ply and one inner ply.