JP5506487B2 - Steel cord and pneumatic radial tire using the same - Google Patents

Description

  The present invention relates to a steel cord (hereinafter, also simply referred to as “cord”) and a pneumatic radial tire (hereinafter, also simply referred to as “tire”) using the steel cord, and more particularly to the productivity of the cord and the fretting wear durability. The present invention relates to a steel cord and a pneumatic radial tire using the same.

  Light weight is one of the important points in tires mounted on small trucks to trucks and buses. For this reason, cords that are as light as possible are used for steel cords used as reinforcing elements for the body plies of these tires.

  As a technique related to the improvement of such a steel cord, for example, Patent Document 1 relates to a steel cord applied to a carcass ply, and in order to achieve both weight reduction and suppression of a reduction in cord strength, the twist pitch of the cord winding wire is 3. A steel cord having an n + m + 1 structure defined as 5 to 5.0 mm is disclosed. According to Patent Document 1, the reduction in cord strength occurs due to wear of the filament material of the cord winding wire and the ply cord. Further, the twisting pitch of the cord winding wire is necessary to make the elasticity within a specified range.

  Further, Patent Document 2 discloses a steel cord with a winding wire with good durability that can sufficiently exhibit the performance of a high tensile strength cord when used as a reinforcing material without causing breakage of the winding wire. . Furthermore, Patent Document 3 discloses a steel cord that has improved durability as well as rubber reinforcement performance and reliability, and further diversified cord characteristics to improve versatility.

JP 2000-96468 A (Claims etc.) JP-A-5-106179 (Claims etc.) Japanese Patent Application Laid-Open No. 11-21776 (claims, etc.)

  However, in the steel cord described in Patent Document 1, the pitch of the cord winding wire is as short as 3.5 to 5.0 mm, which causes a reduction in workability during cord manufacturing. When the pitch of the cord winding wire is increased, the workability at the time of manufacturing the cord is improved, but the elasticity is out of the specified range. If the elasticity is out of the specified range, the end of the carcass ply is disturbed at the time of tire manufacture, resulting in a product defect. Moreover, the carbon content of the steel material of the cord winding wire is the same as that of the steel cord, which has been a factor in reducing productivity in the cord manufacturing process.

  Further, although the steel cords described in Patent Document 2 and Patent Document 3 are effective in improving the durability, the cord productivity and the tire productivity when these steel cords are used as a reinforcing material for the tire. However, the current situation is that further improvement is required.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a steel cord and a pneumatic radial tire using the same that can achieve both the productivity of the cord and the fretting wear durability.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by setting the twist pitch, the carbon content, and the elasticity of the winding wire within a predetermined range. The present invention has been completed.

That is, the steel cord of the present invention is a core made of n (n = 1 to 4) filaments, and 1 formed of m (m = n + (2 to 6)) filaments formed around the core. In a steel cord having an n + m + 1 layer twist structure comprising a sheath of layers and a winding wire wound around the outer peripheral surface of the sheath,
The elasticity is 80 to 90%, the twist pitch p of the winding wire is 5.0 to 10.0 mm, and the carbon content of the steel material of the winding wire is 0.50 to 0.65% It is characterized by being.

In the present invention, the molding rate r of the winding wire is expressed by the following formula with respect to the twist pitch p of the winding wire:
(0.95-0.02 × p) × 100 <r <(1.10−0.03 × p) × 100
It is preferable to satisfy the relationship represented by these. In the present invention, the wire diameter of the winding wire is preferably 0.10 to 0.25 mm. Furthermore, in the present invention, either one or both of the twist pitch and the twist direction of the core and the sheath may be different, or the twist pitch and the twist direction may be the same. Furthermore, in the present invention, the steel material of the core and the sheath has a carbon content of 0.70 to 0.95%, and the filament wire diameter d is 0.10 to 0.30 mm. preferable.

  The pneumatic radial tire of the present invention is characterized by using the steel cord of the present invention as a reinforcing element.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the steel cord which can make the productivity of a cord and fretting wear durability compatible, and a pneumatic radial tire using the same.

It is width direction sectional drawing of the steel cord concerning one suitable embodiment of the present invention. It is explanatory drawing which concerns on the definition of the elasticity of a code | cord | chord. It is explanatory drawing which concerns on the twist pitch of a winding wire. It is explanatory drawing which shows the state which removed the winding wire.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings.
FIG. 1 shows a cross-sectional view of a steel cord according to a preferred embodiment of the present invention. The steel cord 10 of the present invention is formed around a core 1 (three in the illustrated example) composed of n (n = 1 to 4) filaments 11 and around the core 1, and m (m = n + (2 to 2). 6)) a steel cord having an n + m + 1 layer twist structure comprising a single-layer sheath 2 (9 in the illustrated example) composed of the filaments 12 and a winding wire 3 wound around the outer peripheral surface of the sheath 2.

  In the present invention, the elasticity of the steel cord 10 is 90% or less, the twist pitch p of the winding wire 3 is 5.0 to 10.0 mm, and the carbon content of the steel material of the winding wire 3 is 0.50. ~ 0.65%. Thereby, the productivity of the winding wire 3 is improved and the productivity of the cord is improved. Further, while the productivity of the cord is improved, the problem that the cord strength is reduced due to the fretting wear of the winding wire 3 and the cord 10 body can be suppressed to the same extent as before.

  If the elasticity of the steel cord exceeds 90%, the cord body of the winding wire is loosely tightened, the amount of cord movement increases, the fretting wear durability decreases, and the cord strength decreases. In order to obtain the effect of the present invention favorably, the elasticity is preferably 70 to 90%. Moreover, when the twist pitch p of the winding wire 3 is larger than 10.0 mm, even if the shaping ratio r is adjusted, the elasticity cannot be secured, and the tire productivity is lowered. On the other hand, if the twist pitch p of the winding wire 3 is smaller than 5.0 mm, sufficient cord productivity cannot be obtained.

  Here, the elasticity of the code shall conform to the following definition. That is, as shown in FIG. 2, the steel cord 20 is rotated around the steel cord 20 in a free state so as to form a circle having a diameter of 20 cm, and then the point P1 at which the cord intersects is located symmetrically across the center of the circle. The rate of change in the distance between point P1 and point P2 when the circle is crushed in the same plane so that point P2 abuts on point P1 and point P2 is released immediately thereafter ((distance after release) L2 / initial distance L1) × 100) (%) is defined as elasticity. This is an indicator of the degree of tightening of the winding wire cord.

Moreover, the twist pitch p of the winding wire 3 means the length when the winding wire 3 is wound around the sheath 2 as shown in FIG. Further, the molding rate r of the winding wire 3 includes the helical diameter S _A (see FIG. 1) when the winding wire 3 is on the outer peripheral surface of the sheath 2 and the helical diameter S measured with only the winding wire 3 removed. It is defined by the ratio S _B / S _A × 100 (%) with _B (see FIG. 4).

In the present invention, the molding rate r of the winding wire 3 is represented by the following formula with respect to the twist pitch p of the winding wire 3:
(0.95-0.02 × p) × 100 <r <(1.10−0.03 × p) × 100
It is preferable to satisfy the relationship represented by these. By setting the molding rate r in the above range, a desired elasticity, specifically 90% or less, can be ensured even in a region where the twist pitch is long. It is possible to satisfactorily balance fretting wear durability. Further, by using a cord satisfying the above requirements as a carcass ply cord, a tire excellent in formability with less disturbance of the end portion of the carcass ply can be manufactured.

  When the molding rate r of the winding wire 3 is not less than the above range, it may be difficult to ensure elasticity and tire productivity may be reduced. On the other hand, when the molding rate r is less than the above range, there is a possibility that the winding wire 3 may be disconnected at the time of winding, and the code productivity may be reduced.

  Moreover, in this invention, it is preferable that the wire diameter of the winding wire 3 is 0.10-0.25 mm, More preferably, it is 0.10-0.15 mm. When the wire diameter of the winding wire 3 exceeds 0.25 mm, it is not preferable from the viewpoint of weight reduction of the tire. On the other hand, if it is less than 0.10 mm, it is difficult to obtain sufficient cord strength.

  Furthermore, in the present invention, the wire diameter d of the filament constituting each layer of the core 1 and the sheath 2 is preferably in the range of 0.10 to 0.30 mm, more preferably 0.15 to 0.20 mm. When the filament diameter used is less than 0.10 mm, the filament production efficiency is poor. On the other hand, when the filament diameter exceeds 0.25 mm, the filament is subject to fatigue breakage due to excessive bending input to the carcass ply cord. The cord breakage resistance is reduced.

  Furthermore, in the present invention, the carbon content of the steel material of the core and the sheath filament is preferably 0.70 to 0.95%, and more preferably 0.80 to 0.00 from the viewpoint of cord productivity. 90%. By making the carbon content of the steel material of the winding wire 3 smaller than the carbon content of the steel material of the core and the sheath filament, it is possible to satisfactorily suppress the decrease in the cord strength.

  In the present invention, as long as the cord satisfies the above conditions, the conditions relating to the other cord structures are not particularly limited, and the twist pitch and the twist direction are different from each other or both. Or both of them may be the same. For example, the twist pitch of the core 1 can be preferably 5.0 to 7.0 mm, and the twist pitch of the sheath 2 can be preferably 12.0 to 14.0 mm. it can.

  The pneumatic radial tire of the present invention is only required to use the steel cord of the present invention as a reinforcing element such as a carcass ply, and the specific configuration thereof can be appropriately selected according to a conventional method and is particularly limited. It is not something.

Hereinafter, the present invention will be described in more detail with reference to examples.
<Examples 1 and 2, Comparative Examples 1 to 3, Reference Example and Conventional Example>
A 3 + 9 × 0.175 mm + 0.15 mm cord composed of a core composed of three filaments, a single-layer sheath composed of nine filaments, and a winding wire wound around the outer peripheral surface thereof, and a twist pitch of the winding wire It was produced by changing p and the molding rate r as shown in Table 1 below. The twisting pitch p and the molding rate r of the winding wire were changed by previously molding the winding wire before winding.

  For each test cord, the elasticity was measured as described above. Moreover, the code productivity of each test code was evaluated by the following method. The obtained results are also shown in Table 1.

  Further, tires using each test cord as a carcass ply were manufactured at a tire size of 11 / 70R22.5, and evaluated for cord strength and fretting wear durability of the carcass ply cord when new and after running 50,000 km. did. The evaluation method is as shown below.

<Code productivity>
The code productivity is expressed as an index with the length of the cord manufactured per unit time in the process of winding the winding wire as 100 as a conventional example.

<Tire productivity>
As for tire productivity, a green tire using a cord as a carcass ply was produced and left at 50 ° C. for 7 days, and the state immediately after production was compared with the carcass ply shape. Here, it was set as x when the cord end of the carcass ply was changed by 2 mm or more in the direction of jumping up, and when it was less than that, it was marked as ◯. It should be noted that even if the evaluation is ○, if the tire productivity is comparable to that of the conventional example, it is indicated as Δ.

<Strength retention after running and fretting wear durability>
After running, the remaining strength and fretting wear resistance were measured by using the carcass cord for the tire, running the drum at 100,000 km at an internal pressure of 850 kPa and a load of 3 kN, and then removing the carcass cord from the tire to measure the strength and fretting. Wear durability was observed. If the remaining power after running is within 80% of the new product, it is marked as “Good”. The fretting wear durability was evaluated as ◯ when the wear groove depth on the steel cord after removing the winding wire was measured and the wear rate was 20% or less.

<Comprehensive evaluation>
Comprehensive evaluation is ◎ when the elasticity is the same and productivity is particularly excellent compared to the conventional example, ◎, when the elasticity is the same and productivity is excellent, ○, elasticity Are marked with △, and those with poor elasticity and productivity are marked with ×.

※１：型付け率ｒが（０．９５−０．０２×ｐ）×＜ｒ＜（１．１０−０．０３×ｐ）×１００の範囲にある場合○、範囲から外れる場合を×とした。

* 1: When the molding rate r is in the range of (0.95-0.02 × p) × <r <(1.10−0.03 × p) × 100, ○, and when it is out of the range, ×. .

  From Table 1 above, it can be seen that the steel cord of the present invention can achieve both the productivity of the cord and the fretting wear durability.

1 Core 2 Sheath 3 Wound wire 10 Steel cord 11, 12 Filament 20 Steel cord

Claims (7)

a core composed of n (n = 1 to 4) filaments, a single-layer sheath formed around the core and composed of m (m = n + (2 to 6)) filaments, and an outer periphery of the sheath In a steel cord having an n + m + 1 layer twist structure composed of a winding wire wound around a surface,
The elasticity is 80 to 90% , the twist pitch p of the winding wire is 5.0 to 10.0 mm, and the carbon content of the steel material of the winding wire is 0.50 to 0.65% Steel cord characterized by being. The wrapping wire mold forming ratio r is the following formula with respect to the twist pitch p of the wrapping wire:
(0.95-0.02 × p) × 100 <r <(1.10−0.03 × p) × 100
The steel cord according to claim 1, satisfying a relationship represented by:   The steel cord according to claim 1 or 2, wherein a wire diameter of the winding wire is 0.10 to 0.25 mm.   The steel cord according to any one of claims 1 to 3, wherein one or both of a twist pitch and a twist direction of the core and the sheath are different.   The steel cord according to any one of claims 1 to 3, wherein the core and the sheath have the same twist pitch and twist direction.   The steel material of the core and the sheath has a carbon content of 0.70 to 0.95%, and the wire diameter d of the filament is 0.10 to 0.30 mm. Steel cord described in the section.   A pneumatic radial tire using the steel cord according to any one of claims 1 to 6 as a reinforcing element.

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