JP5619360B2 - Steel cords for reinforcing rubber articles and pneumatic tires - Google Patents

Description

  The present invention relates to a steel cord for reinforcing rubber articles (hereinafter also simply referred to as “steel cord”) and a pneumatic tire (hereinafter also simply referred to as “tire”). The present invention relates to a steel cord for reinforcing rubber articles having a double twist structure capable of reducing the creep amount of the circumferential belt, and a pneumatic tire using the steel cord for reinforcing rubber articles as a reinforcing material for the circumferential belt. .

  In general, a pneumatic tire has a carcass layer extending in a toroidal shape between a pair of bead portions as a skeleton, and a belt layer formed by rubberizing various reinforcing elements or a belt reinforcing layer on the outer periphery thereof. The surface portion has a reinforced structure.

  In a steel cord having a double twist structure used as a reinforcing material for a circumferential belt of a pneumatic tire, it is common to twist three strands at a large twist angle. For example, in Patent Document 1, in order to improve the fatigue rupture resistance of the circumferential belt reinforcing layer, the reinforcing cord elastic modulus Ee of the steel cord at the end of the circumferential belt reinforcing layer is set as the reinforcing cord elastic modulus of the steel cord at the center portion. A steel cord having a 3 × (1 × 0.34 + 6 × 0.30) structure, which is set lower than Ec at a certain rate and improves the fatigue rupture resistance of the circumferential belt reinforcing layer, and a tire size of 495 / An example applied to a circumferential belt reinforcing layer of a 45R22.5 heavy-duty pneumatic radial tire is disclosed.

Japanese Patent No. 3983270

  As in the heavy-duty pneumatic radial tire described in Patent Document 1, in order to maintain the shape of the tire, a high-strength cord with a double twist is used as a circumferential belt cord that is a member that acts as a tag in the tread portion. There is a case. Double twisted high elongation cords can be easily stretched, but have the disadvantage that they tend to cause permanent elongation (creep) when a tensile load is maintained for a long time as a steel cord / rubber composite. As a result, when creep occurs during tire application, tire outer periphery growth occurs, which is one of the causes of tire product defects such as tire tread non-uniform wear and tread pattern circumferential groove bottom cracks.

  Accordingly, an object of the present invention is to provide a steel cord for reinforcing a rubber article having a double twist structure that can reduce the creep amount of the circumferential belt when used as a reinforcing material for the circumferential belt of a pneumatic tire, and the rubber article. It is an object of the present invention to provide a pneumatic tire using a reinforcing steel cord as a reinforcing material for a circumferential belt.

  As a result of intensive studies to solve the above problems, the present inventor has found that the above object can be achieved by configuring the steel cord as described below, and has completed the present invention.

That is, the steel cord for reinforcing rubber articles of the present invention is a steel cord for reinforcing rubber articles having a multi-strand structure having 3 to 5 strands and no core strands.
The strand has one or two layers of a core composed of a single core filament and a sheath composed of a plurality of sheath filaments. The diameter of the core filament is d _c (mm), and the diameter of the first sheath filament is d _s1 ( mm), when the diameter of the second sheath filament is d _s2 (mm), the calculated diameter D of the strand is
D _{(C = 1)} (mm) = d _c + 2d _s1 + 2d _s2
And the code diameter calculation value φ (mm)
Code diameter calculated value φ (mm) = D × (1 + 1 / cos (π / 2−π / N))
(Where N is the number of strands in the steel cord),
Strand molding rate (%) = (Strand molding amount (mm)) / (Cord diameter calculation value φ (mm)) × 100
(Here, the strand forming amount (mm) is the full width diameter of the spiral shape of the strand)
In strand typing rate represented (%) is 107 (%) or less, and wherein _{d c} is characterized in that greater than said _{d s1} and the _{d s2.}

  In this invention, it is preferable that the said strand shaping | molding rate (%) is 100 (%) or less.

  The pneumatic tire according to the present invention is characterized in that the steel cord for reinforcing rubber articles according to the present invention is used as a reinforcing material for a circumferential belt.

  According to the present invention, when used as a reinforcing material for a circumferential belt of a pneumatic tire, the steel cord for reinforcing a rubber article having a double twist structure capable of reducing the creep amount of the circumferential belt, and the reinforcing rubber article A pneumatic tire using a steel cord as a reinforcing material for a circumferential belt can be provided.

It is sectional drawing of the steel cord for rubber article reinforcement of 4 * (0.28 + 6 * 0.25) structure of one embodiment of this invention. It is sectional drawing of the steel cord for reinforcing rubber articles having a 5 × (2 + 7) × 0.20 structure according to another embodiment of the present invention. It is sectional drawing of the steel cord for rubber article reinforcement of 3 * (3 + 9 + 15) * 0.15 structure of other embodiment of this invention. It is explanatory drawing of the strand shaping | molding amount.

DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view of an example of a steel cord for reinforcing rubber articles according to the present invention. The steel cord 1 is composed of 3 to 5 (4 in the illustrated example) strands 2 and has a double twist structure having no core strand. The strand 2 has one to two sheaths (one layer in the illustrated example) composed of one to three core filaments 3 (one in the illustrated example) and a plurality (six in the illustrated example) sheath filaments 4. It is comprised by.

In the present invention, when the diameter of the core filament 3 is d _c (mm), the diameter of the first sheath filament 4 is d _s1 (mm), and the diameter of the second sheath filament 4 is d _s2 (mm), the strand 2 The diameter calculation value D of the core filament 3 is one,
D _{(C = 1)} (mm) = d _c + 2d _s1 + 2d _s2
When there are two core filaments,
D _{(C = 2)} (mm) = 2d _c + 2d _s1 + 2d _s2
When there are three core filaments,
D _{(C = 3)} (mm) = 2.1547d _c + 2d _s1 + 2d _s2
And the code diameter calculation value φ (mm)
Code diameter calculated value φ (mm) = D × (1 + 1 / cos (π / 2−π / N))
(Where N is the number of strands in the steel cord),
Strand molding rate (%) = (Strand molding amount (mm)) / (Cord diameter calculation value φ (mm)) × 100
(Here, the strand forming amount (mm) is the full width diameter of the spiral shape of the strand)
It is important that the strand molding rate (%) represented by the formula is 107 (%) or less.

  Creep in a composite composed of a double-stranded steel cord 1 having no core strand and a rubber including the same is formed by a rubber in which a spiral strand 2 exists in the center of the steel cord 1 when the steel cord 1 is loaded. This occurs because the rubber moves from between the strands 2 to the outside of the steel cord 1 during a long time. Therefore, by setting the strand molding rate (%) to 107 (%) or less, the volume space in which rubber enters at the center of the steel cord 1 can be suppressed, and the creep amount of the steel cord / rubber composite is suppressed. can do.

  The strand molding rate (%) is calculated based on the diameter / twisted structure of the core filament 3 and the sheath filament 4, and the steel cord cord diameter calculation value φ (mm) calculated by the above-described definition formula and the strand molding amount (mm) ) (Actual strand 2 spiral diameter (mm)). By reducing the strand molding rate, the volume space in which the rubber in the center of the steel cord 1 enters when the steel cord / rubber composite is formed in the tire can be suppressed. As a result, it is possible to suppress the creep amount of the steel cord / rubber composite that is generated because the rubber is tightened and the rubber moves from between the strands 2 to the outside of the cord for a long time.

  In the present invention, the strand molding rate is preferably 100% or less. When the steel cord / rubber composite is formed in the tire, the volume space in which the rubber enters at the center of the steel cord 1 is minimized, and adjacent strands come into contact with each other. As a result, the tightening action on the rubber that causes the rubber to move from between the strands 2 to the outside of the steel cord 1 is suppressed.

  On the other hand, if the strand molding rate is too small, there may be a problem in the scatter of the ends when the steel cord is cut in tire manufacture. Therefore, the strand molding rate is preferably 50% or more.

The strand shaping amount (mm) can be measured by measuring the full width diameter of the spiral shape of the strand with an optical projector in the state of the steel cord before application of the tire. FIG. 4 is an explanatory diagram for measuring the strand shaping amount (mm). As shown in the drawing, the total widths W ₁ and W ₂ are measured at two locations of the strand 2, and the average value is obtained for each strand 2. And let the average value of the strand shaping amount (mm) of all the strands 2 which comprise the steel cord 1 be the strand shaping amount (mm) of the steel cord 1.

  In the present invention, the number of strands is set to 3-5. When the number of strands is 2, the elongation as a high elongation cord is larger than when the number of strands of the same pitch is 3 or more. This is because it is difficult to obtain. On the other hand, if the number of strands is 6 or more, the size of the space that can be formed at the center of the steel cord is equal to or greater than the strand diameter, the strands are likely to drop, and the twisting properties are likely to be unstable.

  In the present invention, the diameter of the core filament 3 is preferably larger than the diameter of the sheath filament 4. The core filament 3 in the strand 2 is affected only by the spiral processing of the strand, but the sheath filament 4 is further affected by the spiral processing inside the strand. Therefore, the core filament 3 that is less affected by the strength reduction due to the spiral processing is made larger in diameter than the sheath filament 4 and the area ratio of the core filament 3 occupying the cross-sectional area of the steel cord 1 is increased. Can be improved.

  Furthermore, in the present invention, the strand twist angle is preferably 13 to 25 °. By setting the strand twist angle to 13 to 25 °, the breaking elongation of the steel cord can be ensured. When the strand twist angle is less than 13 °, the elongation at break becomes small. On the other hand, when the strand angle exceeds 25 °, the utilization efficiency of the breaking strength of the entire steel cord compared to the breaking strength of the steel filament itself deteriorates. End up. Here, the strand twist angle is an angle formed by the strand helical axis with respect to the longitudinal direction of the steel cord.

  The filament material used in the present invention is not particularly limited, and any conventionally used material can be used. However, the filament material is a high carbon steel having a carbon component of 0.80% by mass or more. preferable. The effect of the present invention can be obtained satisfactorily by making the filament material a high carbon steel having a high hardness carbon component of 0.80% by mass or more. On the other hand, if the carbon component exceeds 1.5% by mass, the ductility is lowered and the fatigue resistance is inferior.

  A steel cord having a strand molding rate of 107% or less, that is, a small strand molding rate according to the present invention can be manufactured by using a tubular stranded wire machine.

Next, the pneumatic tire of the present invention will be described.
The pneumatic tire of the present invention is a pneumatic tire using the steel cord for reinforcing rubber articles of the present invention as a reinforcing material for a circumferential belt. By embedding the steel cord of the present invention in rubber, a circumferential belt with a small creep amount can be obtained, and by applying this to a tire, a pneumatic tire with a small tire outer peripheral length growth can be obtained. .

  The pneumatic tire of the present invention relates to an improvement in the structure of a steel cord used as a reinforcing material for a circumferential belt, and other structures and materials are not particularly limited, and are known structures and Materials can be adopted as appropriate.

Hereinafter, the present invention will be described in more detail with reference to examples.
(Examples 1 and 2, Comparative Examples 1 to 4 and Reference Examples 1 and 2)
Steel cords having a twisted structure shown in Tables 1 and 2 below were produced, and tires having a tire size of 435 / 45R225 were produced using these steel cords as reinforcing materials for the circumferential belt. The strand twist angles were all 19 °. Creep elongation was measured for each of the obtained test tires. The obtained results are also shown in Tables 1 and 2. In addition, the corresponding figure of the used steel cord cross section is shown in FIGS.

(Measurement of creep elongation)
After the tires of Examples 1 and 2 and Comparative Examples 1 to 4 and Reference Examples 1 and 2 were prepared, each test tire was disassembled, and a steel cord was taken out from the tire in a rubber-covered state. The weight was suspended and the creep elongation was measured. The results obtained are shown in Table 1, using Indexes with Comparative Examples 1 for Examples 1, 2 and Comparative Example 2, Comparative Example 3 for Reference Example 1, and Comparative Example 4 for Reference Example 2 as 100. It was written together in 2. The smaller the value, the smaller the creep elongation.

  From Tables 1 and 2, it can be seen that the steel cord for reinforcing rubber articles of the present invention has improved creep elongation.

1 Steel cord 2 Strand 3 Core filament 4 (First and second) sheath filament

Claims (3)

In the steel cord for reinforcing rubber articles of a double twist structure having 3 to 5 strands and having no core strand,
The strand has one or two layers of a core composed of a single core filament and a sheath composed of a plurality of sheath filaments. The diameter of the core filament is d _c (mm), and the diameter of the first sheath filament is d _s1 ( mm), when the diameter of the second sheath filaments was _d s2 (mm), the diameter calculated value D of the strand,
D _{(C = 1)} (mm) = d _c + 2d _s1 + 2d _s2
And the code diameter calculation value φ (mm)
Code diameter calculated value φ (mm) = D × (1 + 1 / cos (π / 2−π / N))
(Where N is the number of strands in the steel cord),
Strand molding rate (%) = (Strand molding amount (mm)) / (Cord diameter calculation value φ (mm)) × 100
(Here, the strand forming amount (mm) is the full width diameter of the spiral shape of the strand)
In strand typing rate represented (%) is 107 (%) or less, and wherein _{d c} is steel cord for reinforcing a rubber article which being greater than said _{d s1} and the _{d s2.}   The steel cord for reinforcing rubber articles according to claim 1, wherein the strand molding rate (%) is 100 (%) or less.   A pneumatic tire, wherein the steel cord for reinforcing rubber articles according to claim 1 or 2 is used as a reinforcing material for a circumferential belt.

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