JP2011235864A - Rubber-cord composite and pneumatic tire using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber-cord composite capable of suppressing torsion without increasing the amount of rubber, and to obtain a pneumatic tire that, by the use of the rubber-cord composite, is light in weight, low in heat generation, and low in rolling resistance while providing improved workability during a tire molding procedure.SOLUTION: A rubber-cord composite 10 is composed of a plurality of tire cords 1 formed of organic fibers and rubber 2 that covers the tire cords 1. The tire cords 1 are composed of S-twist single-direction twist cords and Z-twist single-direction twist cords. The S-twist single-direction twist cord and the Z-twist single-direction twist cord preferably satisfy a relationship expressed by a following expression: 0.4≤s/(s+z)≤0.6 (where s is a total number of S-twist single-direction twist cords and z is a total number of Z-twist single-direction twist cords).

Description

  The present invention relates to a rubber-cord composite and a pneumatic tire using the same (hereinafter, also simply referred to as “composite” and “tire”), and more specifically, a plurality of tire cords made of organic fibers, The present invention relates to a rubber-cord composite composed of rubber to be coated, and a pneumatic tire using the same.

  As a reinforcing material for a pneumatic tire, a treat material made of a rubber-cord composite formed by coating an organic fiber cord with rubber is used. Among them, a treat material made from a single twisted cord that is twisted only in one direction has been conventionally known to have low heat generation properties, and is used to achieve low rolling resistance of tires. .

  For example, in Patent Document 1, as a knit fabric used for a tire cap ply, a polyester twisted cord subjected to a Z twist in the Z direction, and then a twist in the S direction, and a twist in the S direction, Next, a woven fabric in which polyester reverse twisted cords having an upper twist in the Z direction are alternately driven as warps is disclosed. Patent Document 2 uses a polyketone fiber cord formed by twisting a filament bundle made of an aliphatic polyketone as a reinforcing cord for a carcass layer, satisfying predetermined physical properties, and a reinforcing cord for a carcass layer. A pneumatic radial tire in which the twist direction is different for each tire is disclosed.

  Further, in Patent Document 2, as a treating material constituting the belt layer, a rubberized cloth in which organic fiber cords or carbon fiber cords are arranged in parallel in an oblique direction with respect to the tire equator plane, and a steel cord on the tire equator plane. In contrast, the rubber cord is used in an oblique direction and parallel to the direction intersecting the organic fiber cord or the carbon fiber cord, and the twist direction of the belt cords arranged in parallel in the treat material is different for each one. A pneumatic radial tire is disclosed.

JP 2007-070735 A (Claims etc.) JP 2008-044396 A (Claims etc.) JP 2008-044550 A (Claims etc.)

  However, in a single twisted cord, a residual torsional stress is more likely to occur in a treat cord after the rubber is pressure-bonded than in a double twisted cord. For this reason, as shown in FIG. 2, the treatment material 20 itself is strongly twisted by this residual torsional stress. As a result, there is a problem that workability is remarkably deteriorated in the tire molding process, and the process load is large. It was.

  On the other hand, it can be considered that twisting of the treating material is suppressed by giving the treating cord a certain thickness when the treating material is manufactured. However, in this case, there is a problem that the weight of the treating material itself increases due to an increase in the thickness of the rubber, thereby preventing the weight reduction and the low rolling resistance. Therefore, establishment of a technique capable of solving the problem of twisting of the treat material without causing such a problem has been demanded.

  Accordingly, an object of the present invention is to realize a rubber-cord composite capable of suppressing twist without increasing the amount of rubber, and using this, while improving workability in a tire molding process. It is to realize a pneumatic tire having low heat generation and light weight and low rolling resistance.

  As a result of diligent study, the present inventor can solve the above-mentioned problems by mixing S-twisted and Z-twisted cords as tire cords used in the rubber-cord composite constituting the treat material. As a result, the present invention has been completed.

That is, the rubber-cord composite of the present invention is a rubber-cord composite comprising a plurality of tire cords made of organic fibers and rubber covering the tire cord.
The tire cord is composed of an S-twisted piece-twisted cord and a Z-twisted piece-twisted cord.

In the present invention, the S-twisted single twisted cord and the Z-twisted single twisted cord are represented by the following formulas,
0.4 ≦ s / (s + z) ≦ 0.6
It is preferable to satisfy the relationship represented by the formula (wherein s is the total number of S-twisted single twisted cords and z is the total number of Z-twisted single twisted cords). Further, it is preferable that the S-twisted piece-twisted cord and the Z-twisted piece-twisted cord are arranged symmetrically with respect to the center portion in the width direction of the rubber-cord composite.

  Further, in the present invention, it is also preferable that the S-twisted single-twisted cord and the Z-twisted single-twisted cord are alternately arranged one by one at least at the widthwise end portion of the rubber-cord composite. Further, the S-twisted and Z-twisted cords may be alternately arranged in plural, particularly two by two, or alternately one by one. The rubber-cord composite of the present invention is particularly preferably used as a spiral member disposed in the tire circumferential direction.

  The pneumatic tire of the present invention is characterized by using the rubber-cord composite of the present invention as a constituent member.

  According to the present invention, with the above-described configuration, the twist of the rubber-cord composite can be suppressed without increasing the amount of rubber, the workability in the tire molding process is improved, and the heat generation is low and light. Thus, a pneumatic tire with low rolling resistance can be realized.

It is a schematic explanatory drawing which shows an example of the rubber-cord composite of this invention. It is explanatory drawing which shows the twisted state of the conventional rubber-cord composite.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic explanatory view showing an example of the rubber-cord composite of the present invention. As shown in the figure, the rubber-cord composite 10 of the present invention comprises a plurality of tire cords 1 made of organic fibers, four in the illustrated example, and rubber 2 that covers the tire cord 1. In the drawing, the arrow in the tire cord 1 indicates the twist direction of the tire cord 1.

  In the present invention, the tire cord 1 constituting the rubber-cord composite 10 is composed of an S-twisted one-twisted cord and a Z-twisted one-twisted cord. As the tire cord 1 in the rubber-cord composite 10 is mixed with an S-twisted one and a Z-twisted one, the residual stress of the single-stranded cord cancels between the S-twisted one and the Z-twisted one. meet. Thereby, the residual stress acting on the rubber-cord composite 10 can be suppressed, and the twist of the rubber-cord composite 10 can be suppressed. Further, according to the present invention, since it is not necessary to increase the rubber gauge G of the covering rubber 2 as in the prior art, in the tire to which such a rubber-cord composite 10 is applied, weight reduction and reduction of rolling resistance can be realized. Is possible.

In the rubber-cord composite 10 of the present invention, the tire cord 1 may be a mixture of an S-twisted one and a Z-twisted one, but preferably an S-twisted single-twisted cord and a Z-twisted one. The single twisted cord of the following formula,
0.4 ≦ s / (s + z) ≦ 0.6
(In the formula, s is the total number of S-twisted single twisted cords, and z is the total number of Z-twisted single twisted cords). If the ratio of the S-twisted and Z-twisted cords does not satisfy the above range, either one of the twisted cords will be unevenly distributed, and the rubber-cord composite at the time of tire winding molding There is a risk of deteriorating workability such as 10 being warped.

  Further, in the present invention, it is preferable that the S-twisted and single-twisted cords are symmetrically arranged with respect to the center portion in the width direction of the rubber-cord composite 10. Thereby, the effect which suppresses the variation in the characteristic in the width direction both sides of the rubber-cord composite 10 is acquired.

  Furthermore, in the present invention, it is preferable that at least at the end of the rubber-cord composite 10 in the width direction, S-twisted and single-twisted cords are alternately arranged one by one. The end portion in the width direction of the rubber-cord composite 10 has a greater effect on the torsion than the center portion in the width direction. Therefore, an S-twisted cord and a Z-twisted cord are alternately arranged at least in the width direction end portion. By disposing in this manner, it becomes possible to more effectively suppress the occurrence of twisting due to the residual stress canceling effect. Here, in the present invention, the end portion in the width direction of the rubber-cord composite 10 means a portion of 15% of the total width of the rubber-cord composite 10 at both ends in the width direction of the rubber-cord composite 10. .

  Furthermore, in the present invention, it is preferable to alternately arrange a plurality of, in particular, two, S-twisted single-strand cords and Z-twisted single-twist cords, and alternately dispose them one by one. It is also preferable. In this way, the residual stress canceling efficiency can be increased by alternately arranging a plurality of S strands or Z strands of single twisted cords and Z twisted single twisted cords.

  In the present invention, as described above, as the tire cord 1 in the rubber-cord composite 10, it is important only to mix an S-twisted one and a Z-twisted one in an appropriate arrangement. The desired effect of the present invention can be obtained by suppressing the twist of the cord composite 10. The type of organic fiber used for the tire cord 1 in the rubber-cord composite 10, the cord conditions such as the total decitex number of the tire cord 1, the rubber composition of the covering rubber 2, the rubber gauge, and the like can be appropriately determined as desired. There is no particular limitation. The rubber-cord composite 10 of the present invention can be suitably used as, for example, a spiral member disposed in the tire circumferential direction.

  Further, the pneumatic tire of the present invention uses the rubber-cord composite of the present invention as a constituent member of at least one of a carcass, a belt, a cap layer, etc. It can be a pneumatic tire that is excellent in low heat generation and light weight and has low rolling resistance. The tire of the present invention is not particularly limited with respect to the point other than using the rubber-cord composite as a constituent member, and can be appropriately configured according to a conventional method.

Hereinafter, the present invention will be specifically described with reference to examples.
In accordance with the conditions shown in the table below, a rubber-cord composite of each of the conventional examples and each example, each including a plurality of tire cords (material: polyethylene terephthalate (PET)) and rubber covering the tire cords, was produced. . As the tire cord of the conventional example, only a Z twisted single twisted cord was used, and as the tire cord of each example, an S twisted single twisted cord and a Z twisted single twisted cord were used. Further, each rubber-cord composite obtained was applied to two carcass plies, and test tires of conventional examples and examples were manufactured at a tire size of 195 / 65R15.

<Evaluation of workability>
With respect to the rubber-cord composites obtained in the conventional examples and the respective examples, the workability at the time of molding the tire was evaluated by the sensory evaluation of the worker on the basis of the conventional examples.

<Evaluation of weight>
The rubber-cord composite obtained in the conventional example and each example was weighed. The results are shown as an index with the conventional example being 100. The smaller the index value, the lighter and better the rubber-cord composite.

<Evaluation of rolling resistance>
The rolling resistance of the tires obtained in the conventional examples and the respective examples was evaluated. The rolling resistance is set by rotating each test tire on a drum having an outer diameter of 1.7 m under the conditions of an internal pressure of 2.0 kgf / cm ² and a load of 440 kgf, and increasing the rotation speed to 120 km / hour. Then, the drum was coasted, and the moment of inertia at a rotational speed of 80 km / hour was calculated and evaluated based on the following formula. The results are shown as an index with the conventional example being 100. The smaller the index value, the smaller the rolling resistance and the better.
Index value = [(moment of inertia of conventional tire) / (moment of inertia of test tire)] × 100
These results are also shown in the table below.

＊１）式中、ｓはＳ撚りの片撚りコードの総本数であり、ｚはＺ撚りの片撚りコードの総本数である。

* 1) In the formula, s is the total number of S-twisted single twisted cords, and z is the total number of Z-twisted single twisted cords.

  As shown in the above table, the thickness of the rubber-cord composite is equivalent to that of the conventional rubber-cord composite using only the Z-twisted single-strand cord, and the S-strand single-strand cord is used as the tire cord. In the rubber-cord composite of Example 1 using both the Z-twisted and single-twisted cords, it can be seen that the weight is the same and the workability at the time of molding the tire is improved. Further, in the rubber-cord composite of Example 2 in which both the S-twisted single-strand cord and the Z-twisted single-strand cord are used as the tire cord, and the thickness of the rubber-cord composite is made thinner than that of the conventional example. In addition to the workability at the time of tire molding, the weight is also improved. Further, in the rubber-cord composite of Example 3 in which the ratio of the S-twisted and single-twisted cords was changed while the thickness of the rubber-cord composite was made thinner than that of the conventional example, tire molding was performed. The workability at the time is equivalent to the conventional example, and the weight property is improved. Furthermore, in the tires using the rubber-cord composites of Examples 2 and 3 in which the thickness of the rubber-cord composite is made thinner than that of the conventional example, the rolling resistance is reduced compared to the conventional example. I understand that.

  As a result of the above, in each of the examples using both the S-twisted and Z-twisted cords as the tire cords, the tire workability, weight, and rolling resistance are all higher than those of the conventional examples. It was confirmed that good results were obtained.

1 Tire cord 2 Covered rubber 10 Rubber-cord composite

Claims (9)

In a rubber-cord composite composed of a plurality of tire cords made of organic fibers and rubber covering the tire cord,
A rubber-cord composite, wherein the tire cord is composed of an S-twisted single twisted cord and a Z-twisted single twisted cord. The S-twisted single twisted cord and the Z-twisted single twisted cord are represented by the following formulas:
0.4 ≦ s / (s + z) ≦ 0.6
The rubber-cord composite according to claim 1, satisfying a relationship represented by the formula (wherein s is the total number of S-twisted single twisted cords and z is the total number of Z-twisted single twisted cords).   3. The rubber-cord composite according to claim 1, wherein the S-twisted single-twisted cord and the Z-twisted single-twisted cord are arranged symmetrically with respect to the center portion in the width direction of the rubber-cord composite.   The S-twisted single-twisted cord and the Z-twisted single-twisted cord are alternately arranged one by one at least in the width direction end portion of the rubber-cord composite. The rubber-cord composite as described.   The rubber-cord composite according to any one of claims 1 to 3, wherein a plurality of the S-twisted and single-twisted cords are alternately arranged.   6. The rubber-cord composite according to claim 5, wherein two pieces of the S-twisted cord and the Z-twisted cord are alternately arranged.   The rubber-cord composite according to any one of claims 1 to 4, wherein the S-twisted and single-twisted cords are alternately arranged one by one.   The rubber-cord composite according to any one of claims 1 to 7, which is used as a spiral member disposed in a tire circumferential direction.   A pneumatic tire using the rubber-cord composite according to any one of claims 1 to 8 as a constituent member.

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