JPH0698341B2 - Steel cord for tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention reduces air permeability by facilitating the penetration of topping rubber, prevents cord corrosion, and improves tire durability, and The present invention relates to a steel cord for a tire that can reduce the weight of the tire by reducing the weight.

[Conventional technology]

For pneumatic tires for four-wheeled vehicles, especially heavy-duty vehicles such as trucks and buses, and pneumatic tires used for construction vehicles, in order to enhance tire rigidity and support a large tire load, carcass, belt To plies such as layers and bead reinforcing layers, a so-called steel cord in which steel filaments are twisted and embedded in a topping rubber is often used.

As a cord of this kind, generally, as shown in FIG. 4 (a), a core d consisting of three filaments, an inner layer i consisting of nine filaments outside the core d, and an inner layer i Wrapping cord fr on the outside of a three-layer twist structure with an outer layer o consisting of 15 filaments on the outside
3 + 9 + 15 / W type with a circumference of, and Fig. 4 (b)
It is known that a 7 × 7 type composite twist is formed by twisting seven filaments fs to form one strand s and further twisting seven strands s as shown in FIG.

The former 3 + 9 + 15 / W type has a high packing density of cords, so the amount of rubber infiltration during vulcanization is insufficient, and as a result, the air permeability after vulcanization is large, and due to air and moisture inside the tire Rust is likely to occur and durability is poor.

Further, there is a wrapping cord fr provided outside the outer layer o, but this wrapping cord fr and the cord of the outer layer o rub against each other when the tire is deformed, resulting in cord breakage, thereby improving tire durability. Lower.
In the latter case, the filament diameter must be increased in order to maintain the cord strength, and there is a problem that the tire weight is increased as in the former case.

In order to solve one of these problems, a 1 × 27 type, that is, a type in which 27 filaments are co-twisted is also proposed, but such type is compactly twisted and contributes to weight reduction. Although it is possible, the amount of rubber entering at the time of vulcanization is insufficient, and rust is generated, but the above problems have not been completely solved.

A 4 + 9 + 15 three-layer twist structure has also been proposed as shown in FIG. 4 (c), but this one has a larger core c and more voids in the cord than that of FIG. 4 (a). Although the air permeability is decreased by the above, the ply thickness becomes large due to the increase in the cord diameter, and the weight of the tire increases, so that the problem has not been solved yet.

According to the present invention, the filament is formed by four-layer twisting and the combination of the number of twisted filaments of the core and each sheath is regulated, whereby air permeability is increased and strength is increased, and the ply thickness is reduced. The present invention aims to provide a steel cord for a tire that can reduce the weight of the tire and increase the durability of the tire.

[Means for Solving the Problems]

The present invention relates to a steel cord formed by plying steel filaments and coating a topping rubber to form a ply, comprising a core formed by twisting n core filaments, and a core disposed outside the core. And an inner sheath formed by twisting (2n + m) inner filaments around the core, and an intermediate sheath arranged outside the inner sheath and twisted (3n + 2m) intermediate filaments around the inner sheath. And (4n + 3m) outer filaments arranged outside the intermediate sheath and twisted around the intermediate sheath to form a four-layer body, and n is selected from 1, 2, and 3. Is an integer selected from 1, 2 and n is m or more, and the diameter of each filament of the core and the inner, middle and outer layers is ( A steel cord for a tire, in which the diameter of the core filament is ≧ (the diameter of the inner filament) ≧ (the diameter of the intermediate filament) ≧ (the diameter of the outer filament).

[Action]

The steel cord has a twisted structure consisting of four layers, and the number of twisted filaments and the distribution of the outer diameter of the core, inner, middle, and outer sheaths are restricted as described above. The number of twists in the inner, middle, and outer sheaths is reduced, and as a result, the distance between the filaments can be increased, the penetration of rubber into the cord is increased, corrosion resistance is improved, and tire durability is increased. sell.

Further, since the number of core filaments of the core is a small number of 3 or less, the outer diameter of the steel cord becomes small, and therefore the ply can be formed to have a small thickness, so that the tire weight can be reduced.

Further, since it is composed of four layers and no wrapping filament is provided, the filament breakage due to rubbing between the wrapping cord and the outer filament of the outer sheath, which has been apt to occur in the past, does not occur and the durability can be further improved. .

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

As described above, the steel cord 2 is formed by a four-layer twisted structure, and as shown in FIG. 1, a core C in which n core filaments Fc are twisted together in the central portion, and a core C are arranged outside the core C. An inner sheath I formed by twisting (2n + m) inner filaments Fi around the core C and arranged outside the inner sheath I, and (3n + 2m) intermediate filaments Fm surrounding the inner sheath I. It is composed of a twisted intermediate sheath M and an outer sheath O in which (4n + 3m) outer filaments Fo arranged outside the intermediate sheath M are twisted around the intermediate sheath M, where n is 1 or 2 An integer selected from 3, m is an integer selected from 1, and n is m or more.

It should be noted that FIG. 1 exemplifies a 4 + 3 + 8 + 13 + 18 four-layer body formed by setting n = 3 and m = 2.

Such steel cords 2 are reduced by one in the inner sheath I and two in the intermediate sheath M, respectively, as compared with the conventional structure shown in FIG. Gap between filaments Fm and Fm
The gap between the outer filament Fo and the outer filament Fo can be increased respectively to increase the permeability of the topping rubber into the cord, reduce the air permeability, and improve the corrosion resistance. Further, since there is no wrapping cord, the above-mentioned damage is reduced, and it is not necessary to increase the filament diameter in order to maintain the cord strength as compared with that of FIG. .. The number of cores is smaller than that of the three-layer twist shown in Fig. 4 (c), and the air permeability is greatly reduced as a whole without increasing the outer diameter greatly even though it has four layers. it can. Note that the other configuration of the cord of the present invention is
In addition to the above, 3 + 7 + 11 + 15, 2 + 6 + 10 + 14, 2 + 5 +
There are 8 + 11, and 1 + 3 + 5 + 7. When the core filaments are plural, they are twisted together. As shown in the figure, this twisting is a normal twist, and in particular, the straight twisting increases the outer diameter of the core, impairs the stability of the twisted structure, and easily increases the weight.

The diameters dc, di, dm, do of the core filament Fc, inner filament Fi, intermediate filament Fm, and outer filament Fo.
Is set to dc ≧ di ≧ dm ≧ do.

If the diameter of the filament arranged outside is larger than the diameter of the filament located inside it, the gap between the filaments on the outer peripheral side of the cord will be small and the permeability of the topping rubber will be impaired and the air permeability will increase. That means
Not preferable.

In addition, the steel cord 2 having the above-mentioned configuration is each filament Fi, F
The number of twists per unit length is gradually increased toward the same direction and outward toward m and Fo, or twisted as the same. By making the twisting directions the same, the bending rigidity of the cord is increased and manufacturing is facilitated, and the crossing angle between adjacent filaments in the radial direction can be reduced, further reducing the contact pressure between the filaments. It is possible to prevent the cord from being cut.

Next, an example of a pneumatic tire using the steel cord 2 according to the present invention will be described. In FIG. 2, a pneumatic tire 1 includes a tread portion 3, a sidewall portion 4 extending from both ends of the tread portion 3 toward the tire radial direction outer side in the tire radial direction, and a tire radial direction of the sidewall portion 4. The pneumatic tire 1 has a bead portion 5 located at an inner end thereof, and the pneumatic tire 1 has a main body portion 7a extending from the tread portion 3 through the sidewall portion 4 to the bead portion 5a.
And a carcass 7 provided with a turn-back portion 7b that turns back around the bead core 6 of the bead portion 5 from the inner side in the tire axial direction to the outer side, and a belt disposed inside the tread portion 3 and radially outside the carcass. A layer 9 and a bead apex 8 standing up between the winding portion 7b of the carcass 7 and the main body portion 7a from the outer side in the tire radial direction of the bead core 6 as a starting point, and the bead portion 5 A bead portion reinforcing layer 10 for reinforcing the rolled-up portion 7b of the carcass is disposed outside the.

As shown in FIG. 3, the carcass 7 comprises one or more plies P formed by embedding steel steel cords 2 ... In parallel with a topping rubber 12, one in this embodiment. Of the carcass ply 7A, and the steel cord 2 is 70-70 in this example with respect to the tire equator CO.
It is arranged at an angle of 90 °.

Further, the belt layer 9 is composed of one or more of the plies P in which the steel cord 2 is embedded in the topping rubber 12 as in the case of the carcass ply 7A, three belt plies 9A and 9B in this example,
9C is piled up so that the steel cords 2, 2, 2 of each belt ply cross each other. Bead reinforcement layer
The carcass ply 7 is composed of the ply P having the above-mentioned structure in which the steel cord 2 is embedded in the topping rubber 12 like the carcass ply 7A.

As described above, in this embodiment, the carcass ply 7A, the belt plies 9A, 9B, 9C and the bead portion reinforcing layer 10 all use the ply P made of the steel cord 2, but the carcass ply 7A and the three belts are used. Only one of the plies 9A, 9B, 9C and the bead portion reinforcing layer 10 may be formed by the ply P in which the steel cord 2 having the above configuration is interposed.

〔Concrete example〕

Steel cords were prototyped with the configurations shown in FIG. 1 and Table 1, molded into tires, and their performances were tested. The code of the conventional configuration was also tested and compared.

The air permeability is determined by covering each steel cord with a topping rubber, molding it as a tire, and vulcanizing it, then pulling it out from the tire with a certain length of rubber attached, surrounding it with rubber, and 1 kg from one end. The air permeation amount at the other end when an air pressure of / cm ² was applied for 1 minute was measured. The value is shown as an index with Comparative Example 1 as 100. The smaller the value, the better. The cord strength was also measured and the ratio to the cord weight is shown in the column (Cord Strength / Cord Weight) in the table.

As a result of the test, it could be confirmed that all were superior to those of the comparative example.

〔The invention's effect〕 As mentioned above, since the steel cord of the present invention is composed of the four-layer body having the above-mentioned constitution, the strength thereof is great, and by adopting the steel cord of the present invention, the thickness of the ply can be reduced and the tire weight can be reduced. Since the gap between the filaments is larger than that of the filaments, the topping rubber can easily enter, the air permeability becomes small, the corrosion can be reduced, and the durability of the tire can be enhanced.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a sectional view showing an example of a tire using the steel cord of the present invention, FIG. 3 is a perspective view showing a ply, and FIG. ) ~
(C) is a sectional view showing a conventional technique. 12 ... Topping rubber, C ... Core, Fe ... Core filament, Fi ... Inner filament, Fm ... Intermediate filament, Fo ... Outer filament, I ... Inner sheath, M ... Intermediate sheath, O ... Outer sheath, P ... ply.

Claims (3)

[Claims] 1. A steel cord formed by plying steel filaments and coating a topping rubber to form a ply, comprising a core using n core filaments, and a core disposed outside the core. And an inner sheath in which (2n + m) inner filaments are twisted around the core, and an intermediate sheath in which (3n + 2m) intermediate filaments are arranged outside the inner sheath and twisted around the inner sheath. And an outer sheath arranged outside the intermediate sheath and having (4n + 3m) outer filaments twisted around the intermediate sheath 4
In addition to a layered body, n is an integer selected from 1, 2 and 3, m is an integer selected from 1 and 2 and n is m or more, and the core and inner, middle and outer layers are The diameter of each filament is (core filament diameter) ≧ (inner filament diameter)
Steel cord for tires with ≧ (diameter of intermediate filament) ≧ (diameter of outer filament). 2. The number of twists per unit length of the core and each filament of the inner, middle and outer layers is (twist number of core filaments) ≦ (twist number of inner filaments) ≦ (twist number of intermediate filaments) The steel cord for a tire according to claim 1, wherein ≤ (the number of twists of the outer filament). 3. The steel cord for a tire according to claim 1, wherein the filaments of the core and the inner, middle and outer layers have the same twist direction.