JPS63275788A - Large pneumatic 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 large pneumatic tires reinforced with steel cords, particularly to improvements in steel cords used in pneumatic tires for trucks and buses.

[Conventional technology]

Large pneumatic tires that use reinforced steel cords as belts, etc. differ from regular tires in that they have good road performance (BLB resistance) that prevents the occurrence of layer separation (BLB) between the belts when driving on good roads at high speeds. It is said that it is preferable to simultaneously satisfy both of the following performances: and rough road performance (TLB resistance) that suppresses the occurrence of separation (TLB) between the tread layer and the breaker layer when driving on rough roads.

In this regard, conventional steel cords used for the belts of large pneumatic tires were, for example, 3+9+1 as shown in Figure 5.
5 core 9, inner sheath 10, outer sheath 1
There was a steel cord with a three-layer structure consisting of 1.

[Problem that the invention seeks to solve]

However, this type of conventional steel cord having a three-layer structure suffers from rust and deterioration of adhesion due to the intrusion of moisture due to cut scratches, etc., and is unfavorable in terms of BLB resistance and TLB resistance. Furthermore, the wires are likely to wear out when they come into contact with each other, resulting in poor fatigue resistance.

Further, when the belt layer is reinforced, the tread part does not have sufficient rigidity, and has the drawback of being prone to uneven wear.

Therefore, the purpose of this invention is to improve and improve the penetration of rubber into the cord, so that even if the cord is penetrated by moisture caused by nails, stones, cuts, etc. caused by driving on rough roads, the cord can be prevented from entering. The purpose is to prevent moisture from penetrating into the surface, suppress the occurrence of rust, suppress deterioration of adhesive properties, and improve BLB resistance and TLB resistance.

[Means for solving problems]

By the way, if we consider the problems with the three-layer structure of steel cord, the three-layer structure is made up of as many as 27 strands, and the 2.3 sheaths are twisted in different directions.
In addition, due to the absence of rubber, point contact occurs between the sheaths 2 and 3, which tends to cause the strands to wear together, resulting in a lack of fatigue properties.

Therefore, from this point of view, if the number of constituent wires is reduced, the number of contact points between wires is reduced, and the rubber penetrates well,
Wear between the strands can be reduced and fatigue resistance can be improved.

Therefore, in this invention, in order to improve the penetration of rubber, a two-layer structure of a sheath and a core is adopted for the steel cord.
j-fl-Q--dz (dx = diameter of earth wire (mm), dz = diameter of sheath wire (mm), n = number of sheath wires) G of,
The thickness was 0.03 to 0.25 mm, and the core was composed of three strands. When the inter-sheath distance G is less than 0.03 mm, rubber penetration is inhibited, and when it is 0.25 mm or more, the seventh
As shown in the figure, the shape stability after twisting is poor, the sheath wires 12 tend to come into contact with each other on one side, and rubber does not enter. Furthermore, when the number of twisted cores is four or more, the center gap of the core becomes too large, and the intrusion of rubber in this portion becomes a serious problem. On the other hand, if there are two, as shown in Figure 8,
Since the cord core 13 is twisted with two wires, when the wires of the core 13 are arranged horizontally (Fig. 8 (A)) and vertically (Fig. 8 (B)), This phenomenon occurs in the longitudinal direction and occurs every 1/4 pitch, so the bending stiffness differs locally. Especially when applied to tires, the bending stiffness is soft as shown in Figure 8 (A>). In addition to causing concentrated fatigue failure in the cross-section of the horizontal row of cords, the 14 sheathed wires also fall inward from the circumscribed circle of the cord layer, as shown in FIGS. 8(A) and (B). Because it is easy,
This further causes a difference in bending stiffness between the two positions, causing a problem in fatigue resistance.

In addition, in the conventional three-layer structure, wires with a diameter of less than 0.23 mm were used, so the thin diameter of the wires lowered the lateral rigidity of the cord, and when used in belts, the tire tread Because of this, the tires tend to wear unevenly when running. Therefore, in this invention, in order to improve cord rigidity,
By using wires with a diameter of m or more, the rigidity of the tread portion was improved and uniform wearability was improved. Preferably, the wire diameters of the core and sheath are different, and it is appropriate to combine these wires with different diameters.This makes it possible to impart appropriate rigidity, making the tread part more difficult to deform and uneven wear. play.

In order to further improve the fatigue resistance, in addition to improving the rubber penetration, it is important to change the point contact of the sheath cord to a line contact, and therefore it is more preferable to twist in the same direction. In addition, increasing the wire diameter reduces fatigue resistance, but
Carbon content is 0.75~ higher than conventional ・0.72%
It is preferable to use a steel cord having a content of 0.85% because it improves fatigue resistance.

[Effect]

Since this invention is as described above, the rubber penetration is improved, the rubber penetrates well into the cord, and not only does it exhibit sufficient rust resistance, but also the deterioration of adhesion due to moisture etc. is greatly improved. Separation failure between tires is improved, significantly extending tire life. Furthermore, since the cord rigidity is improved, the tread rigidity is increased, so the deformation of the tread portion is small, uneven wear is less likely to occur, and wear performance is further improved. In addition, when the wires are twisted in the same direction, fatigue resistance is further improved because wear and tear between the strands is prevented, and when high carbon steel wire is used, even if the diameter of the strands is increased, fatigue resistance due to abrasion is further improved. There are no problems, and the result is a tire with an extremely long life and high quality, unlike anything before.

〔Example〕

Embodiments of the present invention will be described below in comparison with comparative examples with reference to the accompanying drawings. Table 1 shows the structure, characteristic values, etc. of the steel cords according to the examples and comparative examples.
In addition, the cord is used to reinforce the belt, and the tire 12
The characteristic values of the tire prototyped as 0OR24 are shown.

Example 1 is a tire T-1 using a steel cord consisting of a core 1 and a sheath 2 with a 3+8X0.35 structure as shown in FIG. 1, and Example 2 is a 3X0.36+9 tire as shown in FIG.
Tire-2 using a steel cord consisting of a core 3 and a sheath 4 having an X0.33 structure, Example 3 uses a steel cord consisting of a core 5 and a sheath 6 having a 3X0.34+8X0.36 structure as shown in FIG. This is the tire T-3. Example 4 is a tire T-4 which uses a steel cord having a core and sheath with a 3X8X0.35 structure and whose wire material is 5WR887A, and Example 5 is a 3+8X0.35 tire T-4.
Consisting of 35 cores and sheaths, the wire material is 5WR37
This is a tire T-5 using a 2A steel cord. Further, in Comparative Example 1, the core 7 and sheath 8 have a 3+9X0.33 structure as shown in FIG.
Comparative Example 2, a tire T-6 using a steel cord having a diameter of 0.026 mm, was compared to the conventional 3+ shown in FIG.
9+15X0.23 core 9, inner sheath 10,
This is a tire T-7 using a 3M steel cord consisting of an outer sheath 11.

Table 1 [Note] *Bending Stiffness Index The maximum bending force when one steel cord is bent at the center with a distance of 25 mm between supports is expressed with the cord of Comparative Example 2 as 100.

* Air permeability A steel cord is embedded in the center of a 5Qmm long rubber piece,
Compressed air of 2 kgf/Cm2 was blown from one side, and the amount of air flowing inside the steel cord was measured.

*Tread groove wear amount after 100,000 km of driving on good roads and wear index of 1103 km (lIII &
), and the distance traveled per 1 mm is expressed as an index with Comparative Example 2 set as '100.

*Cord strength retention rate: We disassembled the tire that had been driven for 1103km, removed the belt cord, and measured the strength.

Tire T-7 (Comparative Example 2), which uses the conventional three-layer steel cord shown in Figure 5 for its belt, was tested on rough roads, and the adhesive strength decreased due to moisture infiltration through cut scratches. Separation occurred between belt and tread rubber.

Furthermore, even with a two-layer structure, the tire T-6 shown in FIG. 6 (Comparative Example 1) using a cord with a sheath wire opening 11tiG of less than 0.03 mm has insufficient rubber penetration. Separation between the belts occurred due to moisture ingress through the cuts, making it impossible to renew.

On the other hand, the tires T-1 to T-5 of Examples 1 to 5 had improved rough road performance, and in particular, the carbon content of the strands was 0.75 to 0.75.
Examples 1 to 3 within the range of 0.85% had no failures even when driving on rough roads, and could be updated. In addition, in a driving test on a good road, the tire T-7 of Comparative Example 2 had a soft tread, so it was easily deformed, and step-like wear occurred, and shoulder drop wear occurred in a part of the shoulder. Tires T-1 to T-5 using high cords had a wear index 5 to 8% higher than tire T-7, which was Comparative Example 2, and
The tire life has been improved, and the wear condition is also good. Looking at the cord strength retention rate, in all comparative examples, it is observed that the strength decreases by 7 to 10% due to wear of the strands, but in the examples, the wear is small, 1 to 10%. It is recognized that the decrease is limited to 2%.

Figure 4 is a graph showing the fatigue test results for tire T-5 using 5WR372A wire material with low carbon content.
(Example 5), 5WR38 with relatively high carbon content
T-1 (Example 1) using a 2A wire material has improved fatigue resistance. However, the carbon content is 0.85%
When it comes to tires T-4 using 5WR387A, which exceeds 5WR, there is a tendency for poor road performance to deteriorate.

〔Effect of the invention〕

As described above, the present invention is a large pneumatic tire reinforced with a steel cord composed of two layers, a core and a sheath, and the core of the steel cord is composed of three wires each having a diameter of 0.3 mm or more. and the formula G-(2,1547-dt +
dz) sin "" -dz (d1 = diameter of core wire (mm), d2 = diameter of sheath wire (mm), n =
Since we have adopted a configuration in which the value of the distance G between the sheath wires (expressed by the number of sheath wires) is 0.03 mm to 0.25 mm, rubber penetration into the cord is improved, and rust resistance and other properties are improved. We have been able to provide a large pneumatic tire with significantly improved adhesive strength due to moisture, improved tread belt and separation failure between belts, and significantly improved tire life. In addition, cord rigidity and tread rigidity have also been increased, resulting in less deformation of the tread, less uneven wear, and a rough improvement in wear performance. In addition, in the case of twisting in the same direction, the sheath cord comes into wire contact, which is preferable in terms of fatigue resistance, and if high carbon steel wire is used, the fatigue resistance due to abrasion is significantly improved, resulting in a longer life and higher quality than ever before. We can provide high quality tires.

[Brief explanation of the drawing]

Figure 1 shows the 3+8 used in the embodiment of this invention.
Figure 2 is a cross-sectional view of the cord of the X0.35 structure.
The figure is a cross-sectional view of the cord of the 3X0.34+8X0.36 structure used in the example at
The figure shows the fatigue test results of the cords according to Examples 1 and 5 due to the difference in carbon content, and Figure 5 shows the results of the conventional 3+9+1
Figures 6 and 7 are cross-sectional views of a cord with a 3-layer structure as shown in Figure 5. Figures 6 and 7 are cross-sectional views of a cord with comparative examples of 3+9 and 3+7 structures. Figure 8 is a cross-sectional view of a cord with a comparative example of a 2+7 structure.
A> is a cross-sectional view when the cores are in a horizontal row; (B) is a cross-sectional view when the cores are in a vertical row.

Claims (4)

[Claims] (1) In a large pneumatic tire reinforced with a steel cord composed of two layers, a core and a sheath, the core of the steel cord is composed of three strands with a diameter of 0.3 mm or more, and the formula G = ( 2.1547・d_1+d_2)s
in (180/n) - d_2 (d_1 = diameter of core wire (mm), d_2 = diameter of sheath wire (mm), n =
A large pneumatic tire reinforced with a steel cord, characterized in that the distance G between the sheath wires (number of sheath wires) is 0.03 mm to 0.25 mm. (2) The large pneumatic tire according to claim 1, wherein the carbon content of the strands is 0.75 to 0.85%. (3) A large pneumatic tire according to claim 1 or 2, wherein the core and sheath are twisted in the same direction. (4) A large pneumatic tire reinforced with a steel cord according to claim 1, 2, or 3, wherein the steel cord is applied to the belt.