JP2003011613A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability by suppressing separation caused by metal cords. SOLUTION: A tire reinforcing layer 9 is formed of a sheet body 13 formed by mutually parallel aligning covering cords 12 formed by covering the circumferences of the metal cords 10 with covering rubber layers 11 and covering them with topping rubber G. The covering rubber layer 11 has an organic acid cobalt salt mixed therein and formed of hard rubber with rubber hardness larger than that of the topping rubber G.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire using a cord ply of a metal cord as a reinforcing layer, and by setting the rubber hardness around the metal cord to be larger than the hardness of the topping rubber, the metal cord and its The present invention relates to a pneumatic tire that prevents rubber from peeling in the vicinity and improves durability.

[0002]

2. Description of the Related Art A metal cord is widely used as a rubber reinforcing element from the viewpoint of high cord strength and excellent reinforcing effect. It is used as a reinforcing element for carcasses and belt layers of large tires and belt layers of passenger car tires.

However, metal cords have a problem in adhesion with rubber. Conventionally, the metal cord side is plated with brass and the topping rubber side is mixed with a large amount of organic acid cobalt salt in the rubber. However, this improves the adhesion.

However, although the cobalt salt of an organic acid improves the initial adhesiveness of rubber, it tends to deteriorate and heat age unvulcanized rubber and tends to reduce the heat resistance of topping rubber. Moreover, the organic acid cobalt salt is very expensive, which is disadvantageous in terms of tire cost.

Further, since there is a large hardness difference between the metal cord and the topping rubber covering the metal cord, there is a large difference in the deformation behavior due to running of the tire. Therefore, even if the adhesion between the metal cord and the topping rubber is increased by using the organic acid cobalt salt, the concentration of stress causes the stress to concentrate at the interface between the metal cord and the topping rubber or at the vicinity of the metal cord. Separation easily occurs between the rubbers, and the durability of the ear is impaired.

Therefore, the present invention is based on forming a coating rubber layer containing an organic acid cobalt salt, which is harder than a topping rubber, around the metal cord, and minimizes the amount of the organic acid cobalt salt used. It reduces the cost and prevents the deterioration and heat aging of the topping rubber while ensuring the required adhesiveness, and also provides a gradient in the hardness difference between the metal cord and the topping rubber to reduce the stress concentration, and the separation The purpose of the present invention is to provide a pneumatic tire that has improved durability by suppressing one cycle.

[0007]

In order to achieve the above object, the invention of claim 1 of the present application is a pneumatic tire using a cord ply having a metal cord as a tire reinforcing layer, wherein the cord ply is A sheet-shaped body in which the coated cords formed by covering the periphery of the metal cord with a coated rubber layer are aligned in parallel with each other, and coated with a topping rubber,
Moreover, the coating rubber layer is made of a hard rubber having an organic acid cobalt salt blended therein and having a rubber hardness higher than that of the topping rubber, and the coating rubber layer has a rubber hardness (durometer A hardness) of 65 ° to. 100 °, and the topping rubber has a rubber hardness (durometer A hardness) of 40 °
It is characterized in that it is ˜65 °.

The invention of claim 2 is characterized in that the coating rubber layer has a thickness of 0.1 to 1.0 times the diameter of the metal cord.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below.
This will be described together with the illustrated example. FIG. 1 shows a meridional section when the pneumatic tire of the present invention is for a passenger car.

In FIG. 1, a pneumatic tire 1 includes a carcass 6 extending from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, an inside of the tread portion 2 and an outside of the carcass 6 in a radial direction. Belt layer 7 arranged in
It is equipped with

In the present embodiment, the belt layer 7 of the carcass 6 and the tire reinforcing layer 9 which is the belt layer 7 is formed by the cord ply 21 having the metal cord 10. The carcass 6 has a conventional structure in this example, and the carcass cord is, for example, 75 with respect to the tire equator C.
In this example, one or more carcass plies 6A arranged at an angle of 90 ° to 90 ° are illustrated. The carcass ply 6A includes folding portions 6b, which are folded back from the inside to the outside around the bead core 5, at both ends of the main body portion 6a extending between the bead cores 5 and 5.
A bead apex rubber 8 for bead reinforcement extending from the bead core 5 to the outer side in the tire radial direction in a tapered shape is arranged between a and the folded-back portion 6b. In this example, as the carcass cord, an organic fiber cord such as nylon, polyester, rayon, or aromatic polyamide is used.

Next, the belt layer 7 is composed of two or more, in this example, two cord plies 21A and 21B.

The cord plies 21A and 21B are shown in FIG.
As shown in FIG. 2, a coated cord 12 is used, which is formed by covering the metal cord 10 with a thin coated rubber layer 11. The front and back of a cord array in which the coated cords 12 are aligned parallel to each other are coated with a topping rubber G. It is formed by the sheet-shaped body 13. The metal cord 10 is, in this example,
By arranging at an angle of 15 to 45 ° with respect to the tire circumferential direction and intersecting the plies with each other, the belt rigidity is increased and the tread portion 2 is strongly reinforced with a hoop effect.

The metal cord 10 is not particularly limited, and a wire diameter, a cord diameter, a twisted structure and the like are appropriately selected according to required cord characteristics. That is, it may be a twisted cord formed by twisting a plurality of metal element wires, or a single wire cord formed of one metal element wire, and a bundle structure such as a bundle twist, a layer twist, and an open twist may be adopted. Further, the metal wire may be shaped in a wavy shape or a spiral shape before being twisted.

However, from the viewpoint of adhesiveness to the covering rubber layer 11, it is preferable to subject the metal wire to a conventional plating treatment such as brass plating or zinc plating. FIG. 2 illustrates the case where the metal cord 10 is a brass-plated single-wire cord.

In the coated rubber layer 11,
It is extremely important that the rubber contains an organic acid cobalt salt and is made of a hard rubber having a rubber hardness larger than that of the topping rubber G.

That is, in the present embodiment, as the topping rubber G, a conventional soft rubber having a rubber hardness Hs1 (durometer A hardness) of 40 ° to 65 ° is used for the running characteristics of the tire. In contrast, the coated rubber layer 11
A rubber having a rubber hardness Hs2 of 65 ° to 100 °, preferably 70 ° to 100 ° is used. At this time, the rubber hardness difference Hs2-Hs1 is preferably in the range of 0 to 60 °, and more preferably in the range of 5 to 30 °.

As described above, the intermediate coating rubber layer 11 is interposed between the metal cord 10 and the topping rubber G so that the metal cord 10 and the topping rubber G have a hardness gradient. This makes it possible to reduce the hardness difference between the adjacent metal cord 10 and the covering rubber layer 11 and the hardness difference between the covering rubber layer 11 and the topping rubber G, respectively, and to reduce the difference in deformation behavior during tire running. The stress concentration based on it can be dispersed and relaxed. Therefore, the adjacent surface between the metal cord 10 and the coated rubber layer 11, the coated rubber layer 11
It is possible to effectively suppress not only the surface adjacent to the topping rubber G but also the separation in the topping rubber G.

The thickness TA of the coating rubber layer 11 is the coating thickness T of the topping rubber G on the coating cord 12.
The thickness TA is preferably at least smaller than B, and particularly from the viewpoint of the effect of suppressing separation, the thickness TA is preferably 0.1 to 1.0 times the diameter of the metal cord.

Here, if the rubber hardness Hs1 of the topping rubber G is less than 40 °, it is too soft and inferior in steering stability and durability. On the contrary, if it exceeds 65 °, it is too hard and the same performance (operational stability and durability) is obtained. Sex) is getting worse.

The rubber hardness difference Hs2-Hs1 is 0.
Outside the range of up to 60 °, one of the hardness differences between the metal cord 10 and the coated rubber layer 11 or between the coated rubber layer 11 and the topping rubber G becomes excessive, so that an appropriate hardness gradient can be obtained. As a result, the effect of suppressing separation cannot be fully exerted. When the rubber hardness Hs2 is less than 65 ° or exceeds 100 °, it becomes difficult to set the rubber hardness difference Hs2-Hs1 within the above range.

If the thickness TA of the coated rubber layer 11 is less than 0.1 times the cord diameter, the stress relaxation cannot be sufficiently achieved. On the contrary, if the thickness TA is more than 1.0 times, the thickness of the topping rubber is large. Becomes too thick, and the amount of organic acid cobalt salt used increases, which is disadvantageous for cost reduction.

Next, in order to suppress the separation, it is important to sufficiently secure the adhesiveness between the metal cord 10 and the covering rubber layer 11. Therefore, in the coated rubber layer 11, the organic acid cobalt salt is mixed in the rubber base material.

Here, as the rubber base material, diene rubbers such as natural rubber, isoprene rubber, butadiene rubber, and styrene-butadiene rubber can be preferably used, and these diene rubbers can be used alone or by blending two or more kinds. To use.

As the organic acid cobalt salt, those which have been conventionally used for adhesion to metal cords can be preferably used, and examples thereof include cobalt naphthenate, cobalt stearate, cobalt oleate, cobalt laurate and tridecyl. Cobalt acid, cobalt palmitate, cobalt alanate and the like can be used.

The compounding amount of the organic acid cobalt salt is not particularly limited, but the amount of cobalt is preferably in the range of 0.05 to 1.0 part by weight, preferably 0.05 part by weight, based on 100 parts by weight of the rubber base material. If it is less than 10 parts by weight, it is difficult to maintain the required adhesiveness with the metal cord 10. If it is more than 1.0 parts by weight, further improvement in adhesiveness cannot be expected, and the advantage for cost reduction is small. Become.

Further, in the coated rubber layer 11, in order to secure the above-mentioned high rubber hardness Hs2, 50 to 80 parts by weight of carbon black is blended with 100 parts by weight of the rubber base material as a reinforcing agent. As the other additive, for example, a vulcanizing agent, a vulcanization accelerator, a vulcanization accelerating aid or the like generally used for tire rubbers can be selectively used. Further, in order to obtain the rubber hardness Hs2, it is possible to use a resin material such as resorcin or a resorcin-based resin as an auxiliary, but for reasons of cost, process, etc., do not use these resin materials. Is desirable.

On the other hand, in the topping rubber G, the rubber hardness H
In order to reduce s1, the compounding amount of carbon black is kept within the range of 40 to 60 parts by weight, which is less than that of the covering rubber layer 11, with respect to 100 parts by weight of the rubber base material made of the diene rubber. Since this topping rubber G does not come into contact with the metal cord 10, it is not necessary to mix an organic acid cobalt salt. Therefore, various conventional problems such as deterioration of the topping rubber G, heat aging, and cost increase based on the organic acid cobalt salt can be solved at the same time. Needless to say, other additives such as the vulcanizing agent, the vulcanization accelerator, and the vulcanization acceleration aid can also be selectively used in the topping rubber G.

Next, regarding the method of forming the coated cord 12, the rubber composition containing the organic acid cobalt salt forming the coated rubber layer 11 is once melted into an organic solvent such as toluene to be liquefied. Metal cord 10 in rubber solution
It is possible to preferably employ a method of dipping (dipping) the resin, or a method of using a rubber extruder to simultaneously extrude the metal cord 10 while coating the metal composition with the rubber composition.

In addition to the belt layer 7, the cord ply 21 of this embodiment includes various tire reinforcing layers such as a carcass 6, a band layer (not shown), a bead reinforcing layer (not shown) for reinforcing the bead portion 4. Can be used for

Although a particularly preferred embodiment of the present invention has been described above in detail, the present invention is not limited to the illustrated embodiment and can be modified into various modes.

[0032]

EXAMPLE A tire having a tire size of 195 / 65R15, which uses the cord ply according to the present invention for the belt layer, was prototyped according to the specifications in Table 1, and the durability of each test tire was tested and compared. For the carcass, the following conventional specifications are used. Number of plies (1
Sheet), cord (polyester, 1670dtex), cord angle (89 °)

(1) Tire durability: Using a drum tester, a load of 150% of the maximum load specified in JIS is applied,
And 80k under the pressure of 80% of the internal pressure specified in JIS
Run at a running speed of m / h until the tire is destroyed,
The traveled distance was shown as an index with Comparative Example 1 being 100.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

As described above, according to the present invention, since the coating rubber layer containing the organic acid cobalt salt, which is harder than the topping rubber, is formed around the metal cord, the amount of the organic acid cobalt salt used is minimized. Stop as much as possible, while securing the necessary adhesiveness,
The cost can be reduced and the deterioration and heat aging of the topping rubber can be prevented. Further, since the hardness difference between the metal cord and the topping rubber has a gradient, the stress can be dispersed and relaxed, and in combination with the securing of the adhesiveness, the separation is suppressed and the durability is improved. be able to.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a pneumatic tire of the present invention.

FIG. 2 is an enlarged sectional view showing the cord ply.

[Explanation of symbols]

9 tire reinforcement layer 10 metal cord 11 Covered rubber layer 12 covered cord 13 Sheets 21 cord ply G topping rubber

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tsuru Iizuka             3-6-9 Wakihama-cho, Chuo-ku, Kobe-shi, Hyogo               Sumitomo Rubber Industries, Ltd.

Claims (2)

[Claims] 1. A pneumatic tire using a cord ply having a metal cord as a tire reinforcing layer, wherein the cord ply has a coated rubber layer covering a periphery of the metal cord in parallel with each other. It is a sheet-like body that is aligned and covered with a topping rubber, and the covering rubber layer is made of a hard rubber having an organic acid cobalt salt blended therein and a rubber hardness higher than that of the topping rubber. The rubber layer has a rubber hardness (durometer A hardness) of 65 ° to 100 °, and the topping rubber has a rubber hardness (durometer A hardness) of 40 °.
A pneumatic tire characterized by having an angle of up to 65 °. 2. The coated rubber layer has a thickness of 0.1 to 1.0 times the diameter of the metal cord.
Pneumatic tire described.