JP3359674B2 - Pneumatic tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having a reinforcing steel cord in a belt layer. More specifically, the present invention relates to a pneumatic tire using a steel cord for a belt layer capable of suppressing corrosion propagation due to moisture and the like, improving corrosion propagation resistance, preventing occurrence of a separation phenomenon, and maintaining cord strength.

[0002]

2. Description of the Related Art In a tire having a belt layer reinforced with a steel cord, there is a problem that the durability of the product is shortened due to corrosion of the steel cord filament due to moisture penetrating into the product. For example, if there is a cavity in the steel cord, if the tire tread is damaged enough to reach the belt, the moisture that entered the belt spreads along the length of the cord through the cavity in the steel cord, and as a result Rust caused by moisture also diffuses, and the adhesive strength between the rubber and the steel cord at that portion is reduced, which eventually causes the separation phenomenon.

In order to prevent such corrosion propagation, there has been proposed a cord structure in which rubber sufficiently penetrates into the cord through a gap between adjacent metal filaments by pressure vulcanization. As one of the cord structures, a cord having a so-called 1 + 5 structure in which five sheath filaments are arranged around one core filament has a gap between the sheath filaments, so that rubber easily penetrates, and
JP-A-60-38208 and JP-A-59-1790 disclose highly productive cords that can be twisted in the twisting step.

However, in such a structure, even if the average sheath interval is sufficient, the sheath arrangement is biased, and a portion where the sheaths come into close contact with each other is formed. There was a disadvantage that some parts were not made.

In the 1 + 5 structure as disclosed in Japanese Patent Application Laid-Open No. 56-131404, the core filament diameter is smaller than the sheath filament diameter. However, since the rigidity of the rubber is weak, the effect of the molding is reduced, and even when the molding ratio is increased to improve the permeability of the rubber, the strength is reduced.

Means for increasing the core filament diameter to be larger than the sheath filament diameter, securing a certain gap or more between adjacent sheath filaments, and allowing rubber to penetrate into the inside also increase the weight of the cord, The productivity also deteriorates, and the arrangement of the sheath filaments is partially biased, so that the sheath filaments come into close contact with each other, so that the rubber does not penetrate and sufficient corrosion propagation resistance cannot be obtained.

[0007] Japanese Utility Model Publication No. 56-14396 discloses a steel in which a core wire (core) is bent in a helical shape, and a plurality of side wires (sheaths) are twisted around the core wire in a state where they are not in contact with each other. The code is disclosed. However, according to the research of the present inventor, if the core is bent in a helical shape and a plurality of sheaths are arranged on the outer periphery, this effect cannot be obtained. In order to obtain the corrosion propagation property, it was found that it is important to define the different shaping rate and pitch depending on the number of sheaths and to define the direction of the helix.

Further, in the steel cord having a 3 + 6 structure according to the embodiment of this publication, productivity is poor because the core is composed of three cords, and rubber hardly penetrates into the central part of the three core filaments. Since the space was easily formed and the direction of the molding was not specified in this method, the effect of rubber permeability was questioned.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a structure in which one core filament is spirally formed and 5, 6, 7, and 8 sheath filaments are arranged on the outer periphery of the core filament. These sheath filaments are difficult to contact with each other, yet have good productivity, secure rubber permeability, and use steel cords with improved corrosion propagation resistance while maintaining large cord strength, to provide highly durable tires. It is to provide at low cost.

[0010]

Means for Solving the Problems The present inventor has conducted intensive studies to solve the above-mentioned problems, and as a result, 1 + 5, 1 + 6, 1+
Apply proper molding to core steel filament of 7, 1 + 8 structure, use steel cord that sheath filament is difficult to contact, and stably penetrate enough rubber into steel cord after pressure vulcanization. As a result, the present inventors have found that the present invention can solve the problem and completed the present invention.

That is, the present invention is as follows. (1) In the pneumatic tire, the intersecting belt layer has the following characteristics, and the angle θ between the reinforcing steel cord and the tire circumferential direction is 12 ° ≦ θ ≦ 30 ° Adjacent in the same layer The gap I between the steel cords to be formed is 0.5 mm ≦ I ≦ 2.0 mm, the inter-layer gauge G of the intersecting belt layer is 0.35 mm ≦ G ≦ 2.0 mm, and the reinforcing steel cord has one core steel filament, Consisting of five sheath steel filaments arranged around the core, the core filament is shaped in a spiral and the amplitude L of the spiral shaped is
c and the elementing diameter Rc expressed by the ratio of the element wire diameter dc of the core filament, that is, Lc / dc is 0.12 ≦ Rc ≦ 1.
0, and the spiral molding pitch Pc is 3.0 dc / 0.34 ≦ Pc ≦ 10.0 dc / 0.34
And a crossed belt layer reinforced with a steel cord in which the spiral direction is opposite to the sheath twisting direction.

(2) In the pneumatic tire, the intersecting belt layer has the following features, and the angle θ between the reinforcing steel cord and the tire circumferential direction is 12 ° ≦ θ ≦ 30 ° The same layer The gap I between adjacent steel cords is 0.5 mm ≦ I ≦ 2.0 mm, the inter-layer gauge G of the intersecting belt layer is 0.35 mm ≦ G ≦ 2.0 mm, and the reinforcing steel cord is one core steel. A filament and six sheathed steel filaments disposed around the core, the core filament being spirally shaped, and the amplitude L of the spiral shaping being L
c and the elementing diameter Rc expressed by the ratio of the element wire diameter dc of the core filament, that is, Lc / dc is 0.12 ≦ Rc ≦ 1.
5, and the spiral molding pitch Pc is 3.0 dc / 0.34 ≦ Pc ≦ 10.0 dc / 0.34
And a crossed belt layer reinforced with a steel cord in which the spiral direction is opposite to the sheath twisting direction.

(3) In the pneumatic tire, the crossed belt layer has the following characteristics, and the angle θ between the reinforcing steel cord and the tire circumferential direction is 12 ° ≦ θ ≦ 30 ° The same layer The gap I between adjacent steel cords is 0.5 mm ≦ I ≦ 2.0 mm, the inter-layer gauge G of the intersecting belt layer is 0.35 mm ≦ G ≦ 2.0 mm, and the reinforcing steel cord is one core steel. A filament and seven sheathed steel filaments disposed around the core, the core filament being helically shaped and having an amplitude L of the helical molding.
c and the filament diameter dc of the core filament, the molding rate Rc, that is, Lc / dc is 0.42 ≦ Rc ≦ 1.
8 and the spiral molding pitch Pc is 3.0 dc / 0.34 ≦ Pc ≦ 10.0 dc / 0.34
And a crossed belt layer reinforced with a steel cord in which the spiral direction is opposite to the sheath twisting direction.

(4) In the pneumatic tire, the intersecting belt layer has the following characteristics, and the angle θ between the reinforcing steel cord and the circumferential direction of the tire is 12 ° ≦ θ ≦ 30 ° The same layer The gap I between adjacent steel cords is 0.5 mm ≦ I ≦ 2.0 mm, the inter-layer gauge G of the intersecting belt layer is 0.35 mm ≦ G ≦ 2.0 mm, and the reinforcing steel cord is one core steel. A filament and eight sheath steel filaments disposed around the core, wherein the core filament is shaped in a spiral and the amplitude L of the spiral shaped is
c and the molding rate Rc represented by the ratio of the element wire diameter dc of the core filament, that is, Lc / dc is 0.74 ≦ Rc ≦ 2.
12 and the spiral forming pitch Pc is 3.0 dc / 0.34 ≦ Pc ≦ 10.0 dc / 0.34
And a crossed belt layer reinforced with a steel cord in which the spiral direction is opposite to the sheath twisting direction.

(5) The above-mentioned items (1), (2), (3), and (4) in which a spiral filament is added to the reinforcing steel cord.
The pneumatic tire according to any one of (4).

(6) The carbon steel content of the reinforced steel cord is 0.80 to 0.85% by weight as described in the above items (1), (2),
(3) The pneumatic tire according to any one of (4) and (5).

(7) The core filament diameter dc and the sheath filament diameter ds of the reinforcing steel cord are substantially equal to d.
The preceding paragraphs (1), (2), (3), (4), and c = ds
The pneumatic tire according to any one of (5) and (6).

In the present invention, the angle θ between the embedded steel cord and the tire circumferential direction is set to 12 ° ≦ θ ≦ 30 ° because θ <
When the angle is 12 °, the interlayer shear strain during running of the tire increases, so that separation easily occurs. When θ> 30 °, the circumferential rigidity of the intersecting layer decreases, and the tire grows at the time of internal pressure and running. However, the rubber around the steel cord is distorted and separation is easily caused.

The reason why the gap I between adjacent steel cords in the same layer is 0.5 mm ≦ I ≦ 2.0 mm is that I <0.
When it is 5 mm, the cracks generated at the belt end are connected to each other and spread in the circumferential direction, so that separation is easily generated. When I> 2.0 mm, the rigidity of the cross layer in the circumferential direction is reduced and the internal pressure is reduced. This is because the tire grows in diameter during running and running, causing distortion in the rubber around the steel cord, which tends to cause separation.

Further, the interlayer gauge G is set to be 0.35 mm ≦ G ≦
The reason why 2.0 mm is set is that if G <0.35 mm, the interlaminar shear strain of the interlaminar rubber at the time of running the tire increases, and separation easily occurs. When G> 2.0 mm,
This is because the circumferential rigidity of the intersecting layer is reduced, and the tire grows in diameter at the time of internal pressure and during running, and distortion occurs in the rubber around the steel cord, so that separation tends to occur.

In the present invention, one core filament of the reinforcing steel cord is spirally molded. If one core filament is used, a cavity is formed therein as in the case of a plurality of cores, and rubber does not penetrate. This is because no helical shape is formed, and stress is not concentrated in a helical shape, so that a material having good fatigue resistance and excellent strength can be obtained.

Here, the mold ratio Rc of the core filament is 0.12 ≦ Rc ≦ when there are five sheath filaments.
1.0 When there are 6 sheath filaments 0.12 ≦ Rc ≦
1.5 When there are 7 sheath filaments 0.42 ≦ Rc ≦
1.8 When there are eight sheath filaments 0.74 ≦ Rc ≦
The reason for setting the range to 2.12 is that if Rc is smaller than the value on the left side, the effect of dispersing the sheath arrangement, properly securing the sheath gap, and permeating the rubber into the cord is insufficient.
If c exceeds the value on the right side, the properties of the cord are poor, and when a tensile load is applied to the cord, the stress is not applied uniformly and the strength of the cord is reduced.

The helical forming pitch Pc of the core is 3.0 dc / 0.34 ≦ Pc ≦ 10.0 dc / 0.34
The reason is that if Pc is larger than 10.0 dc / 0.34, the effect of dispersing the sheath arrangement, properly securing the sheath gap, and permeating the rubber into the cord is insufficient.
Is less than 3.0 dc / 0.34, the core filament has a reduced strength due to the load on the core filament during molding, and a uniform load is applied to the core filament and the sheath filament during the tensile load on the cord. And the code strength is reduced. The mold ratio Rc and the helical mold pitch Pc in the present invention are determined by measuring a steel cord taken out from the tire without causing plastic deformation.

The reason why the spiral direction with the core type is set opposite to the sheath twisting direction is that if the twisting is in the same direction, the length of the core in contact with the same sheath filament becomes longer.
The two sheath filaments come into contact with the core, and the portion where rubber does not enter (the upper right portion in FIG. 4) is connected in the longitudinal direction,
The corrosion propagation resistance is deteriorated, and when the tire is injured, the defective adhesion portion is diffused, and separation is likely to occur.

The reinforcing material has a carbon content of 0.80 to 0.85 in order to secure the strength of the tire and reduce its weight.
It is desirable to use steel filaments made of high strength steel by weight. Further, by adding the spiral filament, the shape of the cord cut end can be controlled, and the productivity and the progress of the belt end crack can be improved. When a spiral filament is added, the cord diameter is not significantly affected, and the above advantages are more likely to be obtained. (The spiral filament may or may not be attached.)

When a filament having a core filament diameter smaller than the sheath filament diameter is used, the problem described in paragraph No. 5 occurs. When the core filament diameter is larger than the sheath filament diameter, paragraph No. 6 is used.
The above-mentioned problems occur. Therefore, from the viewpoint of increasing the productivity in the manufacturing process, it is preferable that the core filament diameter dc and the sheath filament diameter ds are substantially equal to each other.

[0027]

EXAMPLES The present invention will be described in more detail with reference to the following Examples and Comparative Examples, but it goes without saying that the present invention is not limited to these Examples. The core mold ratio Rc, core spiral pitch Pc, described in the upper column of Tables 1 to 7,
For trucks and buses of size 750R16, 10.00R20 equipped with a belt including a steel cord having a cord structure, core strand diameter dc, sheath strand diameter ds, sheath twist pitch Ps, core type spiral direction, sheath twist direction. Thirty-four radial tires were prototyped, and the corrosion propagation resistance (separation resistance) and the cord strength of each tire were examined. The results are shown in the lower column of each table. Note that Z and S in the spiral direction and sheath twist direction are JIS G
3510.

The corrosion propagation resistance is as follows: 100 mm of a belt cord covered with rubber is taken out of a tire, and the side is covered with a silicone sealant. After infiltrating the aqueous solution and then immersing for 24 hours, the rubber was pinched off with pliers, the portion where the metal was exposed was regarded as the corrosion propagation portion, and the length (mm) was evaluated. Regarding the separation resistance, a tire that was mounted on an actual vehicle and run on a bad road and completely worn was dissected, and it was confirmed whether or not belt end separation had occurred.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

[Table 3]

[0032]

[Table 4]

[0033]

[Table 5]

[0034]

[Table 6]

[0035]

[Table 7]

In Table 4, Comparative Examples 1 to 5 have a 1 + 5 structure, and Comparative Example 1 has a core type ratio Rc of 0.12.
When it is smaller, the corrosion propagation resistance is inferior to 85 mm. In Comparative Example 2, when the core helical pitch Pc is smaller than 3.0 dc / 0.34, the cord strength deteriorates. Comparative Example 3
When the core type ratio Rc is larger than 1.0, the code strength is deteriorated. Comparative Example 4 had a core helical pitch Pc of 10.
0 dc / 0.34 and the corrosion propagation resistance is 1
Inferior to 00mm. In Comparative Example 5, the core spiral direction was the same as the sheath twist direction, and the corrosion propagation resistance was inferior to 55 mm.

Comparative Examples 6 to 12 have a 1 + 6 structure, and Comparative Example 6 has an inferior corrosion propagation resistance of 100 mm when the core mold ratio Rc is smaller than 0.12. In Comparative Example 7, when the core helical pitch Pc is smaller than 3.0 dc / 0.34, the cord strength is deteriorated. In Comparative Example 8, when the core type ratio Rc is larger than 1.5, the code strength is deteriorated. In Comparative Example 9, the core helical pitch Pc was 10.0 dc /
When it is larger than 0.34, the corrosion propagation resistance is inferior to 100 mm. In Tables 5 and 6, in Comparative Examples 10 and 11, both the cores were not molded, and not only did the corrosion propagation resistance deteriorate, but also the cord strength deteriorated when the sheath wire diameter was reduced. In Comparative Example 12, the direction in which the core was attached was the same as the direction in which the sheath was twisted, and the corrosion propagation resistance was poor.

Comparative Example 13 has a 1 + 7 structure, and has a core type ratio R
When c is smaller than 0.42, the corrosion propagation resistance is poor.
Comparative Example 14 has a 1 + 8 structure, and the core type ratio Rc was 0.74.
If smaller, the corrosion propagation resistance is poor. Comparative Example 15 shows that when the belt angle θ is smaller than 12 °, separation occurs due to tire running. Comparative Example 16 shows that when the belt angle θ is greater than 30 °, separation occurs due to tire running. Comparative Example 17 shows that when the cord gap I is smaller than 0.5 mm, separation occurs due to running of the tire. Comparative Example 18 shows that when the cord gap I is larger than 2.0 mm, separation occurs due to tire running. Comparative Example 19 shows that when the interlayer gauge G is smaller than 0.35 mm, separation occurs due to running of the tire. Comparative Example 2
0 indicates that when the interlayer gauge G is larger than 2.0 mm, separation occurs due to running of the tire.

[0039]

The pneumatic tire of the present invention has good productivity of the steel cord used, is not affected by variations in the manufacturing process, has good corrosion propagation while maintaining cord strength, In addition, since the structure is such that the crack at the end of the belt does not easily propagate, the durability of the tire is improved, and the service life thereof can be greatly improved.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing 1 used in a pneumatic tire of the present invention.
It is the figure which showed 1 sectional drawing of the steel cord of a +5 structure.

FIG. 2 is a cross-sectional view of a steel cord having a 1 + 5 structure used in a conventional tire.

FIG. 3 is a view of a spiral-shaped core filament viewed from a direction perpendicular to a spiral axis, and shows a core element wire diameter d.
It is explanatory drawing of c, spiral amplitude Lc, and spiral pitch Pc.

FIG. 4 is a cross-sectional view showing a portion in which the core spiral direction and the sheath twisting direction are the same and the sheaths are in contact with each other.

FIG. 5 shows 1 used in the pneumatic tire of the present invention.
It is sectional drawing of the steel cord of +6 structure.

FIG. 6 shows 1 used in the pneumatic tire of the present invention.
It is sectional drawing of the steel cord of +7 structure.

FIG. 7 shows 1 used in the pneumatic tire of the present invention.
It is sectional drawing of the steel cord of +8 structure.

FIG. 8 is a cross-sectional view of the center of the crown, taken along a direction perpendicular to one interlaced layer belt cord, illustrating the adjacent cord I and the interlayer gauge G.

[Explanation of symbols]

 1,3 core filament 2,4 sheath filament dc core filament diameter Lc core filament spiral amplitude Pc core filament spiral pitch I adjacent cord gap G interlayer gauge

Claims (7)

(57) [Claims] In a pneumatic tire, an intersecting belt layer has the following characteristics, and an angle θ between a reinforcing steel cord and a tire circumferential direction is 12 ° ≦ θ ≦ 30 ° within the same layer. The gap I between adjacent steel cords is 0.5 mm ≦ I ≦ 2.0 mm, the inter-layer gauge G of the intersecting belt layer is 0.35 mm ≦ G ≦ 2.0 mm, and the reinforcing steel cord is a single core steel filament. And five sheath steel filaments arranged around the core, wherein the core filament is shaped in a spiral and the amplitude L of the spiral shaped is
c and the elementing diameter Rc expressed by the ratio of the element wire diameter dc of the core filament, that is, Lc / dc is 0.12 ≦ Rc ≦ 1.
0, and the spiral molding pitch Pc is 3.0 dc / 0.34 ≦ Pc ≦ 10.0 dc / 0.34
And a crossed belt layer reinforced with a steel cord in which the spiral direction is opposite to the sheath twisting direction. 2. In a pneumatic tire, the intersecting belt layer has the following characteristics, and the angle θ between the reinforcing steel cord and the tire circumferential direction is 12 ° ≦ θ ≦ 30 ° within the same layer. The gap I between adjacent steel cords is 0.5 mm ≦ I ≦ 2.0 mm, the inter-layer gauge G of the intersecting belt layer is 0.35 mm ≦ G ≦ 2.0 mm, and the reinforcing steel cord is a single core steel filament. And six sheath steel filaments arranged around the core, the core filament being shaped in a spiral and the amplitude L of the spiral shaping.
c and the elementing diameter Rc expressed by the ratio of the element wire diameter dc of the core filament, that is, Lc / dc is 0.12 ≦ Rc ≦ 1.
5, and the spiral molding pitch Pc is 3.0 dc / 0.34 ≦ Pc ≦ 10.0 dc / 0.34
And a crossed belt layer reinforced with a steel cord in which the spiral direction is opposite to the sheath twisting direction. 3. The pneumatic tire, wherein the intersecting belt layer has the following characteristics, and the angle θ between the reinforcing steel cord and the tire circumferential direction is 12 ° ≦ θ ≦ 30 ° within the same layer. The gap I between adjacent steel cords is 0.5 mm ≦ I ≦ 2.0 mm, the inter-layer gauge G of the intersecting belt layer is 0.35 mm ≦ G ≦ 2.0 mm, and the reinforcing steel cord is a single core steel filament. And seven sheath steel filaments arranged around the core, the core filament being shaped in a spiral and the amplitude L of the spiral shaping being
c and the filament diameter dc of the core filament, the molding rate Rc, that is, Lc / dc is 0.42 ≦ Rc ≦ 1.
8 and the spiral molding pitch Pc is 3.0 dc / 0.34 ≦ Pc ≦ 10.0 dc / 0.34
And a crossed belt layer reinforced with a steel cord in which the spiral direction is opposite to the sheath twisting direction. 4. In a pneumatic tire, an intersecting belt layer has the following characteristics, and an angle θ between a reinforcing steel cord and a tire circumferential direction is 12 ° ≦ θ ≦ 30 ° within the same layer. The gap I between adjacent steel cords is 0.5 mm ≦ I ≦ 2.0 mm, the inter-layer gauge G of the intersecting belt layer is 0.35 mm ≦ G ≦ 2.0 mm, and the reinforcing steel cord is a single core steel filament. And eight sheath steel filaments arranged around the core, wherein the core filament is shaped in a spiral and the amplitude L of the spiral shaped is
c and the molding rate Rc represented by the ratio of the element wire diameter dc of the core filament, that is, Lc / dc is 0.74 ≦ Rc ≦ 2.
12 and the spiral forming pitch Pc is 3.0 dc / 0.34 ≦ Pc ≦ 10.0 dc / 0.34
And a crossed belt layer reinforced with a steel cord in which the spiral direction is opposite to the sheath twisting direction. 5. The pneumatic tire according to claim 1, wherein a spiral filament is added to the reinforcing steel cord. 6. The reinforced steel cord has a carbon content of 0.8.
The pneumatic tire according to any one of claims 1, 2, 3, 4, and 5, wherein the content is 0 to 0.85% by weight. 7. The core filament diameter dc and sheath filament diameter ds of the reinforced steel cord are substantially equal to dc = d.
The pneumatic tire according to any one of claims 1, 2, 3, 4, 5, and 6, which is ds.