JP2014040679A - Rubber-steel cord composite and pneumatic radial tire including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber-steel cord composite excellent in properties of a treat after coated with rubber and having an M+N structure, and to provide a pneumatic radial tire including the same.SOLUTION: The rubber-steel cord composite includes a plurality of steel cords 10 arranged in parallel and embedded in rubber. The steel cord 10 includes a core comprising M pieces of core filaments 1 and a sheath comprising N pieces of sheath filaments 2 twisted around the core. When the diameter of the core filament 1 is defined as d1 and the diameter of the sheath filament 2 is defined as d2, d1>d2; when the average preforming ratio of the core filaments 1 is defined as H1 and the average preforming ratio of the sheath filaments 2 is defined as H2, H1<H2; and at least one piece of the plurality of steel cords has a twisting direction of the sheath filaments reverse to that of the other steel cords 10.

Description

  The present invention relates to a rubber-steel cord composite and a pneumatic radial tire (hereinafter, also simply referred to as “tire”) using the same, and more specifically, a rubber having an M + N structure having excellent treat properties after rubber coating The present invention relates to a steel cord composite and a pneumatic radial tire using the same.

  Currently, the belt commonly used as the reinforcing member of the carcass that forms the skeleton of the radial tire for passenger cars, especially the reinforcing member of the crown portion of the carcass, is mainly made of a rubberized layer of a steel cord that is inclined with respect to the equator plane of the tire. Two or more steel belt layers are used, and the steel cords in these belt layers intersect each other.

  In recent years, the importance of environmental performance has increased, and there is an increasing need for weight reduction in rubber-steel cord composites (treats) and tires in which steel cords are embedded in rubber as reinforcing members. One technique for reducing the weight of the tire is to reduce the amount of rubber used in the belt treat and to make the belt thinner. However, if the amount of rubber used is reduced, the distance between the cords of the first belt layer and the second belt layer is shortened, so that the rubber peeling starting from the cord end at the end in the belt width direction easily propagates between the cords. In other words, so-called belt edge separation (BES) is likely to occur, and durability is reduced. As a method for improving this BES, a method of making the rubber at the end of the belt thicker than usual is known, but naturally, it increases the weight, which is contrary to the intended weight reduction of the tire. .

  As a technique for reducing the weight of the tire other than reducing the amount of rubber used in the belt treat, it is conceivable to reduce the amount of steel used, for example, to reduce the number of driven steel cords. However, if the number of steel cords to be driven decreases, the rigidity of the belt decreases, which is not preferable. Under such circumstances, many proposals have been made regarding weight reduction and durability improvement of tires. For example, Patent Document 1 proposes a steel cord having an M (M = 2 to 5) + N (N = 1 to 3) structure and the number of filaments M ≧ N for the purpose of reducing the weight of the tire. Yes. Patent Document 2 proposes a steel cord having a 2 + 3 structure for the purpose of improving the durability of the belt. In addition to these, Patent Documents 3 to 7 propose steel cords having a 2 + 3 structure for the purpose of improving various physical properties and workability required as tire reinforcing materials.

  Conventionally, steel cords having an M + N structure have been manufactured with a buncher type twisted wire machine from the viewpoint of productivity. Steel cords manufactured using a buncher type twisting machine are twisted together while imparting reverse torsion (twisting) to the core filament and the sheath filament. Therefore, when a steel cord of M + N structure is covered with rubber to form a rubber-steel cord composite (hereinafter referred to as a treat), if the treat is defeated in the defeating process, the end of the treat will spring up and curl. Workability will deteriorate. Today, Patent Documents 8 to 10 are reported as techniques for reducing such curl of a treat.

JP 2001-98480 A Japanese Utility Model Publication No. 3-128689 JP-A-6-306784 Japanese Patent Laid-Open No. 7-126992 JP 2001-98460 A JP 2006-328557 A JP 2007-63706 A JP-A-8-218283 JP-A-8-325966 JP 9-31874 A

  However, Patent Document 8 is a technique that uses a steel filament instead of a steel cord as a reinforcing material for rubber articles, and Patent Document 9 is a technique for reducing treat curl in a steel cord having a 1 × N single twist structure. Furthermore, Patent Document 10 is a technique for reducing treat curl in a steel cord having a 1 + N layer twist structure. In other words, the techniques proposed in Patent Documents 8 to 10 cannot reduce the curl of the treat when the steel cord having the M + N structure as described in Patent Documents 1 to 7 is used.

  Accordingly, an object of the present invention is to provide a rubber-steel cord composite having an M + N structure and excellent pneumatic properties of a treat after the rubber coating, and a pneumatic radial tire using the same.

  As a result of intensive studies on the structure of the belt in order to solve the above problems, the present inventors have found that in the M + N structure steel cord, the wire diameters of each of the core filament and the sheath filament, the average molding rate, and the steel cord in the rubber The inventors have found that the property of the treat can be improved by using a predetermined arrangement method, and the present invention has been completed.

That is, the rubber-steel cord composite of the present invention is a rubber-steel cord composite in which a plurality of steel cords arranged in parallel are embedded in rubber.
The steel cord is a steel cord comprising a core made of M core filaments and a sheath made of N sheath filaments twisted around the core,
When the diameter of the core filament is d1 and the diameter of the sheath filament is d2, d1> d2, and when the average mold rate of the core filament is H1 and the average mold rate of the sheath filament is H2, H1 < H2, and
At least one of the plurality of steel cords is characterized in that the twist direction of the other steel cord and the sheath filament is opposite.

  In the rubber-steel cord composite of the present invention, it is preferable that 20% or more of the plurality of steel cords have opposite twist directions of the other steel cords and the sheath filament. In the rubber-steel cord composite of the present invention, the plurality of steel cords are preferably formed by alternately arranging two types of steel cords in which the twist direction of the sheath filament is reversed. Furthermore, the rubber-steel cord composite of the present invention preferably comprises a core composed of two core filaments and a sheath composed of 2 to 4 sheath filaments twisted around the core. Furthermore, in the rubber-steel cord composite of the present invention, the H1 is preferably 0% or more and less than 70%. In the rubber-steel cord composite of the present invention, it is preferable that the d1 is 0.16 to 0.32 mm and the d2 is 0.12 to 0.29 mm. Furthermore, in the rubber-steel cord composite of the present invention, the number of the sheath filaments is preferably three.

The pneumatic radial tire of the present invention is disposed on the outer side in the tire radial direction of a carcass formed of at least one carcass layer straddling a toroidal shape between a pair of left and right bead cores and a crown region of the carcass. In a pneumatic radial tire comprising: a tread portion that forms a portion; and a belt that is disposed between the tread portion and the crown region of the carcass and forms a reinforcing portion, and a belt composed of at least two belt layers.
The first belt layer of the first layer and the second belt layer of the second layer of the belt are both made of the rubber-steel cord composite of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the rubber-steel cord composite of the M + N structure excellent in the property of the treat after rubber | gum coating, and a pneumatic radial tire using the same can be provided.

It is a comparison figure of the minor axis of a steel cord, (a) shows the case of d1 = d2, and (b) and (c) express the case of d1> d2. It is explanatory drawing which shows the amplitude of a filament. It is a fragmentary sectional view of a treat, and (a) is a case where H1 <H2, and (b) is a case where H1> H2. It is a half sectional view of a suitable example of the pneumatic radial tire of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The rubber-steel cord composite of the present invention comprises M cores, preferably two core filaments arranged in parallel without being twisted, N cores twisted around the core, preferably 2 A steel cord provided with a sheath comprising four, particularly preferably three sheath filaments, is embedded in a plurality of rubbers. In the steel cord according to the present invention, when the diameter of the core filament is d1 and the diameter of the sheath filament is d2, d1> d2.

  FIGS. 1A to 1C are comparative views of the short diameters of steel cords, where FIG. 1A shows the case where d1 = d2, and FIGS. 1B and 1C show the case where d1> d2. As shown in the figure, the short diameter of the steel cord 10 of the M + N structure (2 + 3 structure in the illustrated example) is governed by the diameter of the sheath filament 2. Therefore, by making the diameter d2 of the sheath filament 2 smaller than the diameter d1 of the core filament 1, the short diameter of the steel cord can be reduced. Therefore, if the steel cord of the present invention is applied to, for example, the reinforcing material of the first belt layer and the second belt layer of the belt constituting the tire, the steel cord of the first belt layer and the steel cord of the second belt layer The thickness of the belt layer can be reduced while maintaining the distance. This makes it possible to reduce the weight of the belt without reducing so-called BES resistance, which is resistance to BES. At the same time, since the amount of steel used can be reduced, the weight of the tire can be further reduced.

Further, the steel cord according to the present invention satisfies the relationship of H1 <H2, where the average mold rate of the core filament 1 is H1 and the average mold rate of the sheath filament 2 is H2. Here, the average molding rate H (%) of the core filament 1 and the sheath filament 2 is the average of the amplitude A of the filaments. When the following formula,
Average molding rate H (%) = Aave. / (2 × d1 + d2) × 100
Defined by Aave., Which is the average of amplitude A Means the average of the maximum value A1 and the minimum value A2 after measuring the amplitude in the filament after unwinding the steel cord. FIG. 2 is an explanatory diagram showing the amplitude of the filament.

  In general, a rubber-steel cord composite that can be suitably used as a material for a belt layer constituting a tire has a large number of steel cords arranged in parallel, and unvulcanized rubber is arranged above and below the steel cord to form a steel cord. Manufactured by rubber coating. In a steel cord 10 having an M + N structure manufactured by a buncher type strand wire machine, the torsion of the core filament 1 and the sheath filament 2 has a torsion in the opposite direction. In particular, the torsion of each filament of the M + N structure having the relationship of d1> d2 is larger than the torsion of each filament in the case of having the relationship of d1 = d2, and has a characteristic that the curl is easily generated in the treat. Yes.

  3A and 3B are partial cross-sectional views of the treat. FIG. 3A shows a case where H1 <H2, and FIG. 3B shows a case where H1> H2. As shown in FIG. 3B, in the case of H1> H2, the core filament 1 is large, so that the core filament 1 moves up and down in the belt cross section, and the core filament 1 and the covering rubber 3a in the longitudinal direction of the steel cord, The site | part which 3b contacts arises. Therefore, the rotation of the core filament 1 is hindered, and the curl of the treat that occurs at the time of the treat break can be prevented. However, as shown in FIG. 3A, when the average molding rate H1 (%) of the core filament 1 is small, the position of the core filament 1 hardly changes, so the core filament 1 comes into contact with the coated rubbers 3a and 3b. In other words, only the sheath filament 2 is in contact with the covering rubbers 3a and 3b. If the treat in this state is broken, the core filament 1 rotates due to the residual torsion, and the sheath filament 2 also has a torsion in the opposite direction to the core filament 1, so these are combined. Will curl.

  Therefore, in the rubber-steel cord composite of the present invention, even if H1 <H2, at least one of the plurality of steel cords embedded in the rubber, preferably 20 of the plurality of steel cords. % Of steel cords and the other steel cords have the opposite twist direction of the sheath filament, thereby reducing the occurrence of treat curl. In other words, the rubber-steel cord composite of the present invention reduces the torsion of the sheath filaments and reduces the curl of the treat by embedding two types of steel cords having sheath filaments with opposite twist directions in the rubber. It is. Particularly preferably, two types of steel cords in which the twisting directions of the sheath filaments are opposite to each other are alternately arranged. When H1 ≧ H2, the core filament comes into contact with the covering rubbers 3a and 3b, and the rotation of the core filament is hindered, so that curling of the treat is difficult to occur. Therefore, the effect of reducing the curl of the treat by canceling the torsion of the sheath filament becomes small.

  In the steel cord which concerns on this invention, it is preferable that the average shaping | molding rate H1 of the core filament 1 is 0 to less than 70%. When H1 exceeds 70%, the core filament 1 moves up and down in the belt cross section (see FIG. 3B), and a portion where the core filament 1 and the covering rubbers 3a and 3b come into contact with each other in the longitudinal direction of the steel cord is generated. In some cases, this reduces the curl reduction effect of the treat by canceling the torsion of the sheath filament. In the rubber-steel cord composite of the present invention, the value of H1 / H2 is preferably 0.70 or less in order to obtain the above-described effects of the present invention satisfactorily.

  In the steel cord according to the present invention, the diameter d1 of the core filament 1 is preferably 0.16 to 0.32 mm, and the diameter d2 of the sheath filament 2 is preferably 0.12 to 0.29 mm. When the filament diameter exceeds the above range, even if the steel cord according to the present invention is used as a belt reinforcing material, a sufficient light weight effect may not be obtained. On the other hand, if the filament diameter is less than the above range, the belt strength may be insufficient. In the steel cord according to the present invention, the d1 / d2 value is set to 1.2 to 2.0 in order to secure the light weight and the belt strength while obtaining the effects of the reduction of the treat curl and the cord property stability. It is preferable.

When the steel cord according to the present invention is used as a belt reinforcing material, it is preferable to use a steel filament having a tensile strength of 2700 N / mm ² or more. As the steel filament having a high tensile strength, one containing at least 0.72% by mass, particularly at least 0.82% by mass of carbon can be suitably used. In the steel cord according to the present invention, conditions such as the twist direction and twist pitch of the sheath filament are not particularly limited, and can be appropriately configured according to a conventional method.

Next, the pneumatic radial tire of the present invention will be described.
FIG. 4 shows a half sectional view of a preferred example of the pneumatic radial tire of the present invention. The illustrated tire includes a tread portion 11 that is disposed in a crown region of the carcass and forms a ground contact portion, a pair of sidewall portions 12 that extend continuously inward in the tire radial direction on both sides of the tread portion 11, A bead portion 13 is provided on the inner peripheral side of each sidewall portion 12.

  The tread portion 11, the sidewall portion 12, and the bead portion 13 are reinforced by a carcass 14 including a single carcass layer extending in a toroidal shape from one bead portion 13 to the other bead portion 13. Further, the tread portion 11 is reinforced by a belt including at least two layers disposed in the tire radial direction outside of the crown region of the carcass 14, in the illustrated example, two layers of the first belt layer 15a and the second belt layer 15b. ing. Here, a plurality of carcass layers of the carcass 14 may be used, and an organic fiber cord extending in a direction substantially orthogonal to the tire circumferential direction, for example, an angle of 70 to 90 ° can be suitably used.

  In the tire of the present invention, both the first belt layer 15a and the second belt layer 15b are made of the rubber-steel cord composite of the present invention. The rubber-steel cord composite of the present invention has reduced work curl, and the cord itself has stable properties, so that it has excellent workability during tire manufacture. Further, by using the rubber-steel cord composite of the present invention, the thickness of the belt layer can be reduced while maintaining the distance between the steel cord of the first belt layer 15a and the steel cord of the second belt layer 15b. This makes it possible to reduce the weight of the belt without reducing so-called BES resistance, which is resistance to BES. Moreover, since the amount of steel used can be reduced, the weight of the tire can be further reduced.

  In the pneumatic radial tire of the present invention, the specific tire structure other than that is not particularly limited as long as the belt structure satisfies the above requirements. Further, the pneumatic radial tire of the present invention can be suitably used for a passenger car tire. In addition, as gas with which a tire is filled, inert gas, such as nitrogen, argon, helium other than the air which adjusted normal or oxygen partial pressure, can be used.

Hereinafter, the present invention will be described in more detail with reference to examples.
<Examples and Comparative Examples>
Steel cords having the structures shown in Tables 1 to 3 below were manufactured using a buncher type twisted wire machine. A treat having a thickness of 1.20 mm was prepared by aligning a plurality of pieces in parallel so as to have the number of implantations shown in the table, and covering the unvulcanized rubber from above and below. The treats of Examples 1 to 5 produced S-twisted steel cords and Z-twisted steel cords, which were alternately arranged. In the treats of Examples 5 to 8, 20%, 50%, 80%, 5% S-twisted steel cord and Z-twisted steel cord were arranged, respectively. All the treats of Comparative Examples 1 to 3 used S-twisted steel cords. Each treat obtained was evaluated for treat curl property and code property stability according to the following procedure.

<Treat curl property>
Each treat obtained was defeated and observed whether the lift occurred in the treat. The results were rated as ◎ when the same level as in Comparative Example 1, ◯ when inferior to Comparative Example 1 but no problem in workability, and x when inferior to Comparative Example 1 and causing problems in workability. The obtained results are also shown in Tables 1-3.

<Code property stability>
Steel cords having the structures shown in Tables 1 to 3 were melted into test pieces having a length of 1 m, and magnified by 20 times using a projector, and the floating of the sheath filament from the core filament was observed. The result was evaluated as ◯ when the same level as in Comparative Example 1 and x when inferior to Comparative Example 1. The obtained results are also shown in Tables 1-3.

<Comprehensive evaluation>
In the evaluation of the treat curl property and the code property stability, ◎ and ○ only are marked with ◎, only ○ is marked with ◯, and x is marked with ×.

  From Tables 1 to 3, it can be seen that the treat produced using the rubber-steel cord composite of the present invention has excellent treat curl properties and the cord properties themselves are stable.

DESCRIPTION OF SYMBOLS 1 Core filament 2 Sheath filament 3a, 3b Cover rubber | gum 10 Steel cord 11 Tread part 12 Side wall part 13 Bead part 14 Carcass 15a 1st belt layer 15b 2nd belt layer

Claims (8)

In a rubber-steel cord composite in which a plurality of steel cords arranged in parallel are embedded in rubber,
The steel cord is a steel cord comprising a core made of M core filaments and a sheath made of N sheath filaments twisted around the core,
When the diameter of the core filament is d1 and the diameter of the sheath filament is d2, d1> d2, and when the average mold rate of the core filament is H1 and the average mold rate of the sheath filament is H2, H1 < H2, and
The rubber-steel cord composite, wherein at least one of the plurality of steel cords has a twisted direction of a sheath filament opposite to that of the other steel cords.   2. The rubber-steel cord composite according to claim 1, wherein 20% or more of the plurality of steel cords has a twisted direction of a sheath filament opposite to that of the other steel cords.   2. The rubber-steel cord composite according to claim 1, wherein the plurality of steel cords are formed by alternately arranging two types of steel cords in which the twist direction of the sheath filament is reversed.   The rubber-steel cord composite according to any one of claims 1 to 3, comprising a core made of two core filaments and a sheath made of 2 to 4 sheath filaments twisted around the core. body.   The rubber-steel cord composite according to any one of claims 1 to 4, wherein the H1 is 0% or more and less than 70%.   The rubber-steel cord composite according to any one of claims 1 to 5, wherein the d1 is 0.16 to 0.32 mm and the d2 is 0.12 to 0.29 mm.   The rubber-steel cord composite according to any one of claims 1 to 6, wherein the number of sheath filaments is three. A carcass composed of at least one carcass layer straddling a pair of left and right bead cores in a toroidal shape, a tread portion disposed on the outer side in the tire radial direction of the crown region of the carcass, and a tread portion; A pneumatic radial tire comprising a belt composed of at least two belt layers, which is disposed between the crown region of the carcass and forms a reinforcing portion.
The first belt layer of the first layer and the second belt layer of the second layer of the belt are both made of the rubber-steel cord composite according to any one of claims 1 to 7. Pneumatic radial tire.

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