JP3359673B2 - 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 belt layer reinforced by a steel cord, and more particularly, to a pneumatic tire having an improved corrosion propagation resistance by suppressing the propagation of corrosion of the steel cord due to moisture and the like. Regarding tires.

[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 filament due to moisture entering the product.

[0003] For example, if there is a cavity in the steel cord of a tire, and if the tire tread is damaged enough to reach the belt, moisture penetrating the belt travels along the cavity in the steel cord and extends along the longitudinal direction of the cord. Spread,
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.

First, Japanese Patent Publication Nos. 62-2164 and 60
JP-A-49421 discloses that an excessively large mold gives a gap to a filament of a cord. However, there is a disadvantage that it is difficult to maintain the gap and the effect is affected by handling in the tire manufacturing process.

On the other hand, Japanese Patent Application Laid-Open No. 1-175503 discloses a technique for improving a cord structure to secure a gap between filaments, irrespective of the molding of the core filament. A steel cord made of filament was proposed.
178204 and JP-A-2-15486 disclose a two-layer twisted steel cord comprising a core made of two metal wires and a sheath filament disposed around the core.

In particular, the 1 + 6 cord disclosed in Japanese Patent Laid-Open Publication No. 1-175503 can be twisted in one step, which is advantageous in productivity. However, in the disclosed 1 + 6 cord, the core filament diameter is made larger than the sheath filament diameter to secure a certain gap or more between adjacent sheath filaments so that the rubber penetrates into the inside. In particular, when the sheath filaments are biased, the rubber does not penetrate on the side where the sheath filaments are in close contact with each other, and when applied to truck tires running on severe high moisture bad roads, sufficient corrosion resistance propagation I can not get the nature. Further, there are problems such as an increase in cord weight and a decrease in productivity.

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, so that the gap between the sheath filaments becomes narrower, rubber hardly enters, and the rigidity of the core increases. Is weakened, the effect of waveform shaping is reduced,
Further, there is a disadvantage that the strength is reduced even when the mold ratio is increased to improve the permeability of the rubber.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the rubber permeability of the conventional 1 + 6 structure cord as described above, and further to improve the 1 + 7 and 1 + 8 structure steel cords which have been difficult to penetrate the rubber. An object of the present invention is to provide a tire having a high separation resistance at a low cost by using a steel cord having a 1 + 6, 1 + 7, and 1 + 8 structure whose corrosion propagation resistance is improved by increasing rubber permeability.

[0010]

Means for Solving the Problems The present inventor has conducted intensive studies to solve the above-mentioned problems, and as a result, 1 + 6, 1 + 7, 1+
By using a filament having substantially the same diameter as the sheath filament as the core filament of the eight-structure steel cord and applying an appropriate corrugation to the core filament, sufficient rubber can be stabilized on the steel cord after pressure vulcanization. The present invention was completed.

That is, the present invention is as follows. (1) In a 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 ° Adjacent steel in the same layer The gap I between the cords is 0.5 mm ≦ I ≦ 2.0 mm, the interlayer gauge G is 0.35 mm ≦ G ≦ 2.0 mm, and the reinforcing steel cord is disposed around a core made of one steel filament and the core. The core filament is shaped into a waveform, and the shaping rate Rc (= the ratio of the amplitude Lc of the waveform shaping to the strand diameter dc of the core filament) is provided. Lc / dc) is 0.12 ≦
Rc ≦ 1.5 and the pitch Pc of the waveform shaping
However, assuming that the core filament diameter is dc, 3.0 dc /
A pneumatic tire having a crossed belt layer reinforced with a steel cord in which 0.34 ≦ Pc ≦ 10.0 dc / 0.34.

(2) 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 °. A gap I between adjacent steel cords is 0.5 mm ≦ I ≦ 2.0 mm, an interlayer gauge G is 0.35 mm ≦ G ≦ 2.0 mm, and the reinforcing steel cord is formed of a single steel filament, and a periphery of the core. The core filament is corrugated, and the shaping rate is represented by the ratio of the amplitude Lc of the corrugation and the wire diameter dc of the core filament. Rc (= Lc / dc) is 0.48 ≦
Rc ≦ 1.86 and the pitch Pc of the waveform shaping
However, assuming that the core filament diameter is dc, 3.0 dc /
A pneumatic tire having a crossed belt layer reinforced with a steel cord in which 0.34 ≦ Pc ≦ 10.0 dc / 0.34.

(3) 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 °. A gap I between adjacent steel cords is 0.5 mm ≦ I ≦ 2.0 mm, an interlayer gauge G is 0.35 mm ≦ G ≦ 2.0 mm, and the reinforcing steel cord is made of one steel filament, and a core is formed around the core. The core filament is shaped in a waveform, and the shaping rate is represented by the ratio of the amplitude Lc of the waveform shaping to the strand diameter dc of the core filament. Rc (= Lc / dc) is 0.98 ≦
Rc ≦ 2.36 and the pitch Pc of the waveform shaping
However, assuming that the core filament diameter is dc, 3.0 dc /
A pneumatic tire having a crossed belt layer reinforced with a steel cord in which 0.34 ≦ Pc ≦ 10.0 dc / 0.34.

(4) The pneumatic tire according to any one of (1) to (3), wherein a spiral filament is added to the reinforced steel cord.

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

(6) The above items (1), (2), (3), wherein the core filament diameter dc and the sheath filament diameter ds of the reinforced steel cord are substantially dc = ds.
The pneumatic tire according to any one of (4) and (5).

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 <12.
When ゜, the interlayer shear strain during tire running becomes large, so that separation easily occurs, and θ
If it is> 30 °, the circumferential stiffness of the intersecting layer will decrease, the tire will grow in diameter at the time of internal pressure and running, and the rubber around the steel cord will be distorted, which will easily cause separation.

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 easily occurs. When I> 2.0 mm, the rigidity of the cross layer in the circumferential direction is reduced, and This is also because the tire grows in diameter during 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, the core filament of the reinforced steel cord is shaped into a corrugation. This waveform is 1 + 6, 1
It is important that the steel cord of each structure of +7, 1 + 8 has a waveform with a specific range of amplitude and pitch.
By this, a gap of rubber permeation is secured between the sheath filaments. However, since this waveform has good productivity and low cost, and the core filament is corrugated, the cord itself becomes a flat cord. Thus, an increase in the number of cord layers due to molding can be prevented, the gauge can be made thinner, the rubber layer can be made thinner, and heat generation of the tire can be suppressed and weight can be reduced. Further, since the rubber has good permeability, there are advantages such as an increase in corrosion resistance.

Here, the typed waveform is preferably a waveform having a gentle curve such as a sine wave rather than a shape having a sharp vertex such as a triangle, and the stress is concentrated at the vertex. Can be prevented.

When the number of sheath filaments is 6, ie, 1
In the case of the +6 structure, the core filament molding rate Rc
(= Lc / dc, where Lc is the amplitude of the waveform, and dc is the diameter of the core filament wire), and 0.12 ≦ Rc ≦ 1.5.
If Rc is less than 0.12, the effect of dispersing the sheath arrangement, properly securing the sheath gap, and penetrating the rubber into the cord is insufficient, and if Rc exceeds 1.5, the cord properties are poor. This is because, when a tensile load is applied, the stress is not applied uniformly and the cord strength is reduced.

When the number of sheath filaments is 7, that is, 1
In the case of the +7 structure, the core filament type ratio Rc
Is set to 0.48 ≦ Rc ≦ 1.86. When Rc is smaller than 0.48, there is the same defect as when Rc <0.12 when 1 + 6, and when Rc exceeds 1.86, it is the same as when Rc> 1.5 when 1 + 6. There are drawbacks.

When the number of sheath filaments is eight, ie, 1
In the case of the +8 structure, the core filament molding rate Rc
Is set to 0.98 ≦ Rc ≦ 2.36. When Rc is smaller than 0.98, there is the same disadvantage as when Rc <0.12 when 1 + 6, and when Rc exceeds 2.36, it is the same as when Rc> 1.5 when 1 + 6. There are drawbacks.

The corrugated patterning pitch Pc of the core filament
For each of the structures 1 + 6, 1 + 7, and 1 + 8, 3.0 dc / 0.34 ≦ Pc ≦ 10.0 dc / 0.
34. 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 smaller than 3.0 dc / 0.34, the core filament has a reduced strength due to the load on the core filament at the time of molding, and a uniform load is applied to the core filament and the sheath filament during the tensile load on the cord. Without taking
Insufficient code strength.

As a reinforcing material, when the strength of the tire is ensured and the weight is reduced, the carbon content is 0.80 to 0.85.
It is preferable to use a steel cord made of a high-strength steel material 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 the diameter of the core filament is smaller than the diameter of the sheath filament, the interval between the sheath filaments becomes narrower, rubber hardly enters, and the rigidity of the core becomes weaker, so that the effect of molding is reduced. When the core filament diameter is larger than the sheath filament diameter, there are problems such as an increase in cord weight and a decrease in productivity. Therefore, in order to increase the productivity in the manufacturing process,
It is preferable that the core filament diameter dc and the sheath filament diameter ds are substantially the same.

[0028]

The present invention will be described more specifically with reference to the following examples and comparative examples, but the present invention is not limited to these examples. Table 1, Table 2, Table 3, Table 4,
The core filament diameter dc, sheath filament diameter ds, cord structure, core waveform shaping rate Rc described in Table 5,
Size 10.00 with belt embedded steel cord with core corrugated pitch Pc sheath twist pitch Ps
Twenty-three R20 truck and bus radial tires were prototyped, and the corrosion propagation resistance (separation resistance) of each tire was examined. The results are shown in Tables 1 to 5 below.

The corrosion propagation resistance was determined by taking out a 100 mm belt cord with the rubber covered from the tire, coating the side surface with a silicone sealant, immersing one end of the cord in a 10% NaOH aqueous solution, and applying an aqueous solution only from the cut surface. After immersion for 24 hours, the rubber was pinched with pliers and peeled off. The portion where the metal was exposed was regarded as the corrosion propagation portion, and the length (mm) was evaluated. Separation resistance is
The tire was mounted on an actual vehicle, and was run on bad roads to dissect completely worn tires, and the occurrence of belt end separation was checked.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

[0033]

[Table 4]

[Table 5]

In Comparative Example 1, the core filament had a molding rate of less than 0.12, and the corrosion propagation resistance was as poor as 100 mm. In Comparative Example 2, the pitch Pc of the core waveform was 3.0 dc.
/0.34 less, the cord strength is 182kgf
And inferior. Comparative Example 3 is the case where the core type ratio is larger than 1.5, and the cord strength is inferior to 180 kgf. Comparative Example 4 is a case where the pitch Pc of the core waveform is larger than 10.0 dc / 0.34, and the corrosion propagation resistance is as poor as 100 mm. Comparative Examples 5 and 6
In each case, no corrugation is applied to the core filament, and the corrosion propagation resistance is poor.

Comparative Example 7 has a 1 + 7 structure in which the core mold ratio is smaller than 0.48, and the corrosion propagation resistance is inferior. Comparative Example 8 has a 1 + 8 structure, in which the core mold ratio is less than 0.98, and the corrosion propagation resistance is poor. Comparative Example 9 shows that when the belt angle θ is smaller than 12 °, separation occurs due to tire running. Comparative Example 10 has a belt angle θ of 3
If it is larger than 0 °, it indicates that separation occurs due to running of the tire. Comparative Example 11 shows that when the cord gap I is smaller than 0.5 mm, separation occurs due to running of the tire. Comparative Example 12 has a code gap I
Is larger than 2.0 mm, it indicates that separation occurs due to tire running. Comparative Example 13 shows that when the interlayer gauge G is smaller than 0.35 mm, separation occurs due to running of the tire. Comparative Example 14 shows that when the interlayer gauge G is larger than 2.0 mm, separation occurs due to running of the tire.

[0036]

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]

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

FIG. 2 is a sectional view of a conventional steel cord having a 1 + 6 structure (having a large core diameter and no molding).

FIG. 3 is a cross-sectional view of a corrugated surface of a core formed into a corrugated steel cord used in the pneumatic tire of the present invention, and shows a core wire diameter dc, a waveform amplitude Lc, and a waveform pitch P.
It is explanatory drawing of c.

FIG. 4 is a sectional view of a steel cord having a 1 + 7 structure used for the pneumatic tire of the present invention.

FIG. 5 is a sectional view of a steel cord having a 1 + 8 structure used for the pneumatic tire of the present invention.

FIG. 6 is a cross-sectional view of a crown center portion of a tire cut perpendicularly to one cross layer belt gauge, and is an explanatory diagram of an adjacent cord gap I and an interlayer gauge G;

[Explanation of symbols]

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

Claims (6)

(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 circumferential direction of the tire 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 interlayer gauge G is 0.35 mm ≦ G ≦ 2.0 mm, and the reinforcing steel cord is formed of a single steel filament core. A sheath formed of six steel filaments arranged, wherein the core filament is shaped in a waveform, and a shaping rate represented by a ratio of an amplitude Lc of the waveform shaping to a wire diameter dc of the core filament. Rc (= Lc / dc) is 0.12 ≦ R
c ≦ 1.5 and the pitch Pc of the waveform shaping is
Assuming that the core filament diameter is dc, 3.0 dc / 0.
A pneumatic tire having a crossed belt layer reinforced with a steel cord satisfying 34 ≦ Pc ≦ 10.0 dc / 0.34. 2. In a pneumatic tire, an intersecting belt layer has the following characteristics, and an angle θ between a reinforcing steel cord and a circumferential direction of the tire is 12 ° ≦ θ ≦ 30 °. The gap I between the steel cords to be formed is 0.5 mm ≦ I ≦ 2.0 mm, the interlayer gauge G is 0.35 mm ≦ G ≦ 2.0 mm, and the reinforcing steel cord is formed of a single steel filament core. A sheath formed of seven steel filaments arranged, the core filament being shaped in a waveform, and a shaping rate Rc represented by a ratio of an amplitude Lc of the waveform shaping to a wire diameter dc of the core filament. (= Lc / dc) is 0.48 ≦
Rc ≦ 1.86 and the pitch Pc of the waveform shaping
However, assuming that the core filament diameter is dc, 3.0 dc /
A pneumatic tire having a crossed belt layer reinforced with a steel cord in which 0.34 ≦ Pc ≦ 10.0 dc / 0.34. 3. The pneumatic tire, wherein the intersecting belt layer has the following characteristics, and an angle θ between the reinforcing steel cord and the circumferential direction of the tire is 12 ° ≦ θ ≦ 30 °. The gap I between the steel cords to be formed is 0.5 mm ≦ I ≦ 2.0 mm, the interlayer gauge G is 0.35 mm ≦ G ≦ 2.0 mm, and the reinforcing steel cord is made of a single steel filament. A sheath formed of eight steel filaments arranged, the core filament being shaped in a waveform, and a shaping rate Rc represented by a ratio of an amplitude Lc of the waveform shaping to a wire diameter dc of the core filament. (= Lc / dc) is 0.98 ≦
Rc ≦ 2.36 and the pitch Pc of the waveform shaping
However, assuming that the core filament diameter is dc, 3.0 dc /
A pneumatic tire having a crossed belt layer reinforced with a steel cord in which 0.34 ≦ Pc ≦ 10.0 dc / 0.34. 4. The pneumatic tire according to claim 1, wherein a spiral filament is added to the reinforcing steel cord. 5. The reinforcing steel cord having a carbon content of 0.5.
The pneumatic tire according to any one of claims 1, 2, 3, and 4, wherein the content is 80 to 0.85% by weight. 6. The core filament diameter dc and the 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, and 5, which is ds.