JPS63256782A - Radial tire - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to improvements in steel cords for reinforcing tires, which can be used in carcass plies, chavers, belts, etc., particularly in radial tires.

(Prior art) A conventional steel cord of this type is 2 shown in Fig. 3.
A +7 structure, a 3+9 structure shown in FIG. 4, or a 1×12 structure shown in FIG. 5 were used.

(Problems to be Solved by the Invention) However, in the steel cord 3 with the 2+7 structure shown in FIG. The cross-sectional portions arranged vertically (Fig. 3B) and the cross-sectional portions arranged horizontally (Fig. 3A) are exposed in the longitudinal direction, and due to the twisted structure, the cross-sectional portions are 1/4
Since each pitch has this structure, there are parts with different bending stiffness on the same cord.
Concentrated fatigue failure occurs in the horizontal cross-sectional area shown in >. In addition, as shown in the figure, the side element wire 5 constituting the side 7 tends to fall inward from the circumscribed circle of the core 6 due to its structure, so the side element wire 5 that constitutes the side 7 tends to fall inward from the circumscribed circle of the core 6. As a result of the line 5a sinking to the position shown by the solid line, the vertical
The difference in bending stiffness between the cross-sections in the horizontal rows became even more remarkable, posing a major problem in fatigue resistance. In addition, when embedded in rubber, all the wires in this structure are covered with rubber, making it difficult for air pockets mixed in during tire molding to travel inside the steel cord and disperse to the outside, resulting in air pockets remaining. However, when the tires are manufactured as they are, they have the problem of being easily affected by this when the tires are running, resulting in premature failure.

On the other hand, in the case of the steel cord 3 having a 3+9 structure, as shown in FIG. There was a problem in that the wires 5 abraded due to contact with each other, resulting in deterioration of fatigue resistance.

In addition, as shown in Figure 5, in the case of a steel cord with a 1 x 12 structure, 12 strands of the same diameter are twisted in the same direction and at the same pitch. As a result, the intrusion of rubber is inhibited, and the core wire 4 tends to be easily pulled out while the tire is running.

As described above, none of the conventionally constructed steel cords satisfies the requirements of uniformity of bending stiffness and intrusion of rubber in a well-balanced manner throughout the cord.

Therefore, the purpose of this invention is to eliminate the bending rigidity change that occurs at regular pitches in the longitudinal direction of the steel cord and caused by changes in the cross-sectional structure, as in the past, and to have good rubber penetration. Another object of the present invention is to provide a radial tire reinforced with steel cords having a structure in which contact between each strand is alleviated.

(Means for Solving the Problems) In order to solve the above-mentioned problems, this invention aims to solve the problems by specifically specifying each component of the steel cord's cross-sectional structure, twisting direction, and twisting bits.

In other words, if rubber infiltration is more than necessary, air pockets generated during tire manufacturing will remain as described above, and if this cord is used in a tire, the tire will become defective and cause separation in a short period of time even when the tire is driven. On the other hand, if the rubber penetration is insufficient, wear occurs due to contact between the strands, resulting in fatigue and rust.

Therefore, it is important to provide a structure that resolves both of these contradictions; an internal structure that provides air permeability to the extent that air pockets generated during tire vulcanization do not remain during tire manufacturing, and to the extent that early failures do not occur. It is necessary to control the intrusion of rubber.

Therefore, as a means of achieving this, the diameters of the strands constituting the steel cord are approximately the same, the core and side layers are twisted in the same direction, and twisted at different pitches, and the core is composed of 3 to 4 strands. The side layer was made of steel cord consisting of a number equal to or less than the number of core strands + 5. The reason why the core and side layers are twisted in the same direction is that if the twisting direction is the same, the crossing angle between the core and side pixel lines can be made smaller, and the contact pressure between the core and side strands can be reduced. This is because it leads to improvement in fatigue resistance.

In addition, the structure in which the strands are twisted at different pitches means that the 8th side is twisted at the same pitch,
This is because if the cords are twisted in the same direction, as shown in FIG. 5, the cross section of the cord will result in insufficient penetration of rubber due to the structure. It is preferable that the twisting pitch is larger on the sides compared to the core, and the optimum side pitch:core pitch is 2:1, but each twist is 5:1.
A change of about 0% is suitable.

The reason why the core is made up of 3 to 4 strands is that if there are 2 cores, as mentioned above, there will be a difference in bending stiffness in the longitudinal direction, and air will accumulate frequently due to air impermeability. The city is empty. In addition, if there are five cores, the area of the void formed at the center of the core becomes too large for rubber to enter, and as a result, more air passes through than necessary, making it more likely to rust. Therefore, in this invention, the number of cores is 3 to 4 as a means to maintain appropriate air permeability. Also, on the side, the number of core strands + 5
The reason for setting the number to be equal to or less than is for the following reason. In other words, in order to increase the strength of the cord, it is appropriate to increase the number of cores on the side by +6, and therefore, as shown in Figure 4, it becomes 3 + '1 fen, but as mentioned above, the penetration of rubber is insufficient. In order to facilitate rubber penetration, we adopted a structure in which the upper limit is +5 instead of 16.

Therefore, the structure of the steel cord that can be adopted in this invention is 3+1.3+2.3+3.3+4.3+5.3+
6.3 + 7.3 + 8.4 + 1.4 + 2.4 + 3.4 + 4
．． The structure is 4+5.4+6.4+7.4+8.4+9.

(Function) Since this invention is as described above, the permeability of rubber into the inside of the steel cord is moderately improved, and the air permeation, which was caused by excessive rubber permeation as in the past, is eliminated. There is no longer a problem with air accumulation in the tire and the resulting separation caused by short-term driving, and contact wear between wires due to excessive air permeation, fatigue, and rusting caused by insufficient penetration of rubber are eliminated. Also, since the twisting direction is the same, the contact pressure between the core and side strands is reduced, reducing fatigue due to abrasion.Furthermore, since the bending rigidity is uniform in the longitudinal direction, extreme fatigue does not occur.

In short, when the tire is cured, the rubber is sufficiently infiltrated into the cord without causing any defects in air accumulation, and while maintaining breathability, which prevents fatigue and rusting and improves durability. It can be made into a long-life radial tire.

〔Example〕

Example 1 Four types of steel cords shown in Table 1 were made.

A is a steel cord having a core 1 and side 2 layer of a 3+8 structure as shown in FIG. 1, and B, C, and D are conventional examples or steel cords as shown in FIGS. This is a steel cord having a core 6 and side 7 layers with a 3+9.2+7.5+6 structure according to a comparative example. Note that FIG. 2 shows a 4+81 Ma steel cord according to another embodiment.

Below is a margin.Next, 11R22,5 radial tires were prototyped using the above code for the plies, Example TA, Comparative Examples TB, TC,
A prescribed test was conducted as TD. The results are as follows. The results are expressed as an index with the value of Comparative Example TB set as 100.

Margin below * Strength retention rate ratio Each tire was installed on a route truck and removed after driving 100,000 km, the ply cord was taken out, the strength was measured, the strength retention rate was calculated relative to the strength of the new tire, and the strength retention of the TB was determined. Value with the rate as 100.

As is clear from the table, in the tire according to the example using code A, the steel cord maintains appropriate air permeability and appropriate rubber penetration is obtained, so there is no problem with air pockets during tire manufacture. Because of this, it has a high separation and durability in the drum test, and has excellent fatigue resistance.

On the other hand, in the comparative example, the air permeability was not appropriate and the rubber penetration was poor, so the tire durability was poor.

Example 2 Next, the ply material of Example 1 was applied to a chamber, and 1'1
I made a prototype of R22.5 tie A7 and tested it. The results are shown in Table 3.

Table 3 *Values when the drum test run was performed by filling the internal pressure with 6.0 kM cm2 and applying a load of 260% of the JISVJ weight, and the running time of the CB was set as 100.

As is clear from the table, Tire CC uses Steel Cord C, so the rubber is excessively infiltrated, which causes air pockets during tire vulcanization, resulting in bead separation and durability. Deterioration is observed.

Also, as with tire CD, undesirable results occur if the air permeation is too large. On the other hand, the tire CA according to the example has a preferable value in terms of durability.

Example 3 Next, we investigated cords that were different from the cords used in Examples 1 and 2, with different diameters and the like. The steel cords are those shown in Table 4.

Table 4 Next, this cord was tested by reinforcing the belt of a 120OR24 radial tire. The results are shown in Table 5.

Since the tire neck openings in Table 5 had the same twisting direction and the same twisting pitch, poor penetration of the rubber occurred, and the core strands were pushed out toward the shoulder. In addition, in Tire T, the separation spreads from the air reservoir, causing belt separation, and in some cords, the core element wire is 5. m
It was found here and there that it was bent along the m width. On the other hand, in the case of Tire A according to this example, since the reason for the test suspension was a tube puncture, there was no problem with the tire itself, and it was recognized that the durability was improved.

〔Effect of the invention〕

As described above, the steel cord according to the present invention has appropriate air permeability, the penetration of rubber into the interior of the cord is also appropriate, the contact pressure between the core and the side strands is low, and there is little abrasion. , no air pocket defects occur during tire vulcanization,
Furthermore, fatigue and rusting can be prevented, resulting in a tire with a longer life than conventional tires.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a steel cord used in an embodiment of a radial tire according to the present invention, Fig. 2 is a sectional view of a steel cord used in an embodiment of the radial tire, and Figs. FIG. 6 is a cross-sectional view showing an example of a steel cord. FIG. 6 is a cross-sectional view showing a comparative example.

Claims (1)

[Claims] (1) In a radial tire reinforced with steel cord consisting of two layers: core and side, the core has 3 to 4 strands of wire,
The sides are constructed with a number equal to or less than the number of strands in the core + 5, and all the strands have approximately the same diameter, and the core and sides are reinforced with steel cords twisted at different pitches and in the same direction. A radial tire characterized by: