JP2000016021A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic radial tire which avoids cord rupture of a belt in good performance, achieves a long lifetime of a tire, and accomplishes a lightweight construction. SOLUTION: The carcass of a pneumatic radial tire consists of plies including radially arranged cords stretching in troidal form between a pair of bead parts, and at least two layers of belts are provided on the outside in radial direction of the crown part of the carcass, wherein each cord is composed of a plurality of filaments including steel filaments whose ruptural elongation is over 3.5%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pneumatic radial tire, and more particularly to a pneumatic radial tire having excellent durability.

[0002]

2. Description of the Related Art In general, pneumatic radial tires have the following characteristics.
A carcass composed of plies of a radially arranged cord extending in a toroidal shape between a pair of bead portions is used as a skeleton, and a belt and a tread are sequentially arranged outside a crown portion of the carcass. Each of the carcass and the belt is formed by covering a large number of cords arranged in parallel with rubber, and the cords are formed at an angle of substantially 90 ° with respect to the tire equator in the carcass and 0 to the tire equator in the belt. It is customary to arrange each at an angle of 30 °. Then, the tension in the tire width direction caused by the internal pressure filling is borne by the carcass, while the tension in the tire circumferential direction is borne by the belt.

Here, as a cord for reinforcing the belt,
For example, in passenger car tires, steel filament 2
1 × 2, 1 × 3, 1 × 4 twisted up to 5 strands simultaneously
And around a single twisted structure represented by a 1 × 5 structure and a core in which two steel filaments are twisted,
A layer twist structure represented by a 2 + 7 structure in which seven steel filaments are twisted to arrange a sheath is used. In the case of truck / bus tires, 6 cores are wound around a core of three steel filaments.
A layer twist structure represented by a 3 + 6 structure in which a sheath is arranged by twisting steel filaments and a 1 + 6 structure in which a sheath of six filaments is provided around one core is used. Further, in a construction vehicle tire, a sheath is arranged by twisting nine steel filaments around a core in which three steel filaments are twisted, and a sheath of 15 filaments is further provided outside the sheath. And wrapping filaments wrapped around it, 3 + 9 + 15 +
7 × 7 + in which seven layers of a layer-twisted strand represented by one structure and a layer-twisted strand of a 1 + 6 structure are simultaneously twisted, and one wrapping filament is wound therearound.
A multiple twist structure represented by one structure is used.

[0004]

However, due to recent social demands for resource saving and energy saving, even for heavy duty tires, development of tires with low rolling resistance which contributes to lower fuel consumption of automobiles, that is, lighter tires, Is required. On the other hand, from the user's side, it is required to extend the life of the tire in consideration of economy.

[0005] To reduce the weight of the tire, it is effective to reduce the amount of cords used in the belt, that is, to reduce the number of cords driven by the belt. If a large impact is applied to the belt due to the tire riding on the stones or obstacles on the road, the cord with the reduced number of strikes easily breaks the cord, further breaks the cord, lowers the belt strength, and eventually reduces the tire strength. Will lead to shorter life.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a pneumatic radial tire that advantageously avoids breakage of a cord of a belt, extends the life of the tire, and can reduce the weight.

[0007]

The inventors of the present invention have repeatedly studied various cords and tires, and as a result, the above-mentioned problems have been solved by applying a steel cord composed of a specific filament to a belt. Headline,
The present invention has been completed.

The gist configuration of the present invention is as follows. (1) A pneumatic radial tire having a carcass composed of plies of a radially arranged cord extending in a toroidal shape between a pair of bead portions as a skeleton, and having at least two layers of belts on a radially outer side of a crown portion of the carcass. A pneumatic radial tire characterized in that at least one layer of the belt is made of a cord comprising a plurality of filaments including a steel filament having a breaking elongation of 3.5% or more.

(2) The pneumatic radial tire according to the above (1), wherein the steel filament is subjected to a bluing treatment after drawing.

(3) The pneumatic radial tire according to (1) or (2), wherein the carbon content of the steel filament is 0.6 to 1.0 wt%.

(4) In the above (1), (2) or (3),
A pneumatic radial tire with a steel filament diameter of 0.10 to 0.40 mm.

(5) In the above (1), (2), (3) or (4), at least two belt layers, in which cords are arranged crosswise between belt layers, have a breaking elongation of 3.5% or more. A pneumatic radial tire using a cord, composed of a plurality of filaments including a steel filament.

[0013]

FIG. 1 illustrates a specific example of a radial tire for a passenger car according to the present invention. The tire has a carcass 2 extending in a toroidal shape between a pair of bead cores 1, and a belt 3 having at least two layers, two layers in the illustrated example, disposed outside a crown portion of the carcass 2 in the tire radial direction.
And a tread 4 disposed radially outward of the belt 3 in the tire radial direction. The belt 3 is formed by covering a large number of cords arranged in parallel with rubber, and arranging the cords at an angle of 10 to 30 ° to the tire equator and in a direction in which the cords intersect between the layers. Become. And
It is characterized in that at least one layer of the belt 3, preferably at least two layers in which the cords are intersected between the layers, is applied with a cord made of a steel filament having a breaking elongation of 3.5% or more.

That is, in order to avoid breakage of the cord due to impact applied to the belt and breakage of the cord, which is a problem when the number of steel cords driven into the belt 3 is reduced, a steel filament having a breaking extension of 3.5% or more is used. It is essential that at least part of the code is constructed. Because the elongation at break of the steel filament
By making it 3.5% or more, when an impact is applied to the cord of the belt under severe use conditions, it becomes possible to absorb this impact force within the increased breaking energy of the filament, thereby breaking the cord and eventually breaking the cord. This is because it can avoid.

Here, the steel filament having a breaking elongation of 3.5% or more is preferably applied to at least a part of the filaments constituting the cord, specifically, to at least half of the filaments, more preferably to all the filaments. It is recommended that

The breaking elongation of the steel filament is
To achieve 3.5% or more, it is advantageous to apply a bluing treatment to the filament drawn by drawing with a die. Specifically, after performing wire drawing a plurality of times, for example, three times at a constant area reduction rate, a plating process,
Next, a bluing process is performed in which the film is kept at, for example, 340 to 460 ° C. for a short time of several seconds to several tens of seconds. Then, using the filament subjected to the bluing treatment, the cord is twisted into, for example, a 1 + n or 1 × n structure to form a cord. Further, after a filament that has been plated after a plurality of wire drawing operations is twisted to form a cord, the cord may be subjected to the same bluing treatment as described above. In any case, it is preferable to increase the adhesion to rubber by performing an acid treatment after the bluing treatment.

By the way, the tensile strength of the filament is
3000MPa or more, preferably 3500MPa or more,
Recommended for reducing tire weight and rolling resistance by reducing the number of cord shots.

The structure of the cord is not particularly limited as long as it is composed of a steel filament having a breaking elongation of 3.5% or more, but the following cord structure is advantageously applicable.
That is, in a tire for a passenger car, 1 × n (n: 2 to 7)
1 + n (n: 5 to 8), 2 + n (n: 5)
11), 3 + n (n: 6 to 12), 1 + n + m (n: 5 to 5)
8, m: 9 to 15), 2 + n + m (n: 5 to 11, m: 11 to)
17) A layer twist structure of 3 + n + m (n: 6 to 12, m: 12 to 18) can be adopted. In truck / bus and light truck tires, 1 × n (n:
8 to 27), and in a construction vehicle tire, in addition to the above structure, nxm (n: 2 to 7,
m: 2 to 27). In either structure, the wrapping filament can be wound around. Also, in the layer twist structure, the core filament may be corrugated or helically shaped. is there.

Next, the diameter of the filament is 0.10 to 0.40 mm.
It is preferable that Because the filament diameter is 0.
If it is less than 10 mm, the belt strength will be low, so it will be necessary to increase the number of cords to be driven into the belt, which will hinder the weight reduction of the tire, and will also reduce the gap between the cord end faces exposed at the end of the belt ply, reducing the cord Since the separation between the cord and the rubber is connected to each other at the end faces of the cord and the separation proceeds, which causes a reduction in belt end separation resistance, the thickness is set to 0.10 mm or more, more preferably 0.15 mm or more. On the other hand, if the filament diameter exceeds 0.40 mm, the amount of bending strain increases when the cord is subjected to extreme bending input, and as a result, corrosion fatigue occurs in the cord of the outermost layer of the belt and the layer inside the belt, especially on rough roads This can cause breakage of the code.

Further, it is preferable that the carbon content of the steel filament is 0.6 to 1.0 wt%. That is, if the carbon content of the filament is less than 0.6 wt%, the tensile strength of the filament becomes small, and the number of driving in the belt must be increased to secure a predetermined belt strength. As a result, the weight reduction and belt end separation resistance of the tire are impaired. On the other hand, if the carbon content of the filament exceeds 1.0 wt%,
It is not practical because the ductility of the filament decreases and the wire drawing processability deteriorates.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Belt 3 of a radial tire for a passenger car having the structure shown in FIG.
Then, a steel cord manufactured under the specifications shown in Tables 1 and 2 was applied, and a tire having a size of 195 / 75R14 was prototyped. Here, the belt 3 has a two-layer structure in which steel cords are arranged on the carcass 2 at an angle of 20 ° with respect to the equatorial plane of the tire and arranged so that the cords intersect between the layers. The steel cord applied to the belt 3 composed of the two crossed belt layers has a 1 × 3 structure shown in FIG.
The 1 + 6 structure shown in FIG.

The tires thus obtained were examined for impact crush resistance, cord breakage in belt ply and belt end separation resistance, and wire drawing workability. The results of these surveys are also shown in Tables 1 and 2. The evaluation results are shown based on the comparative examples in each table.

Here, since the impact fracture resistance has a correlation with the plunger energy, the plunger energy was used as an index. That is, the test tire was mounted on a standard rim, filled with an internal pressure of 240 kPa, and left at room temperature for 3 hours or more. Then, attach the tire to the testing machine, align the tip of the plunger (diameter: 19 mmφ) with the center of the tread of the tire, check the air pressure (240 kPa), and then remove the plunger at a load speed of 50 ± 2.5 mm / min. Push into the tire and measure the plunger travel and pushing force.
It was recorded on an XY recorder, and the breaking energy was calculated by moving distance (cm) until the tire was broken and pushing force (kg). The average of the fracture energies at five equally spaced points on the circumference of one tire was taken as the fracture energy of each tire, and the result was evaluated by the impact fracture index determined by the following equation. (Impact fracture resistance index) = (Destruction energy of each tire) /
(Fracture energy of comparative example) x 100

The above-mentioned test tires are mounted on a standard rim, filled with an internal pressure of 200 kPa, mounted on an actual vehicle, and run at a speed of 60 km / h on a zigzag bent road for 20,000 km. The number of cords broken in the belt by dissecting the tire was measured, and the result was indicated by an index when the measured value of the comparative example was set to 100. The smaller the index is, the smaller the number of cord breaks is, and the more excellent the cord break resistance is.

Since the belt end separation resistance is governed by the crack length at the end of the belt ply, this crack length was used as an index of the belt end separation resistance. In other words, the test tires described above were incorporated into a standard rim, filled with an internal pressure of 150 kPa, and then mounted on an actual vehicle, and were run on a general road for 60,000 km under a load corresponding to the maximum load capacity.
Thereafter, the tire was dissected, the crack length at the end of the innermost layer of the outermost layer of the belt was measured, and the result was indicated by an index when the crack length in Comparative Example was set to 100. The smaller the index is, the smaller the crack length is, indicating that the belt end separation resistance is excellent.

The drawability was measured by measuring the number of breaks that occurred during the drawing of the filament and expressed as an index when the value of Comparative Example was set to 100. The smaller the index, the smaller the number of times of disconnection, indicating that the wire drawing is more excellent.

[0027]

[Table 1]

[0028]

[Table 2]

From the comparison between the invention examples and the comparative examples in Tables 1 and 2, it can be seen that the belt made of a cord of filaments having a breaking elongation of 3.5% or more according to the present invention particularly improves the resistance to impact. In the conventional steel cord, the elongation at break of the filament was about 1.8%. However, in the present invention, the same filament as that constituting the conventional steel cord was subjected to a bluing treatment so that the filament was broken. The growth was significantly increased to 3.5% or more. Inventive Examples 3 and 9 are examples in which the filament diameter is 0.08 mm, and Inventive Examples 4 and 10
Is an example having a filament diameter of 0.44 mm, Invention Examples 5 and 11 are examples having a carbon content of 0.50 wt%, and Invention Examples 6 and 12 are examples having a carbon content of 1.10 wt%.

Embodiment 2 As shown in FIG. 3, a carcass 2 extending in a toroidal shape between a pair of bead cores 1 and a cord of 10 to 30 ° with respect to the equator of the tire, on the tire radial outside of the crown of the carcass 2 A steel cord is applied to a belt 3 of a truck / bus tire composed of a four-layer belt 3 arranged at an angle and a tread 4 arranged radially outward of the belt 3 to apply a tire having a size of 10.00 R20 14PR. Prototype made. The steel cord used was a 1 + 6 structure shown in FIG. 4 (a) and a 2 + 6 + 11 structure shown in FIG. 4 (b). Also,
The belt 3 has a steel cord on the carcass 2 in the order of the first, second, third and fourth belts from the radially outer side with respect to the equatorial plane of the tire. Second and third tilted at a 20 ° angle
When the cords between the belt layers are intersected and arranged in a four-layer structure, and when the cords of the second and third belts have a 1 + 6 structure, the remaining two layers also have a 1 + 6 structure, while the second and third belts have When the cord had a 2 + 6 + 11 structure, the remaining two layers had a 1 + 6 structure. The specifications of the cords of the second and third belts are shown in Tables 3 and 4, and conventional steel cords were used for the cords of the other layers.

With respect to the tire thus obtained, impact resistance, impact resistance of the cord in the belt ply, belt end separation, and wire drawing were examined. The results of these surveys are shown in Tables 3 and 4. The evaluation results are shown based on the comparative examples in each table.

Here, since impact resistance has a correlation with plunger energy, plunger energy is used as an index. That is, the test tire was mounted on a standard rim, filled with an internal pressure of 725 kPa, and left at room temperature for 3 hours or more. After that, the tire was mounted on the testing machine, the tip of the plunger (diameter: 19 mmφ) was matched with the center of the tread of the tire, the air pressure (725 kPa) was checked, and then the plunger was loaded at a load speed of 50 ± 2.5 mm / min. Push into the tire and measure the plunger travel and pushing force.
It was recorded on an XY recorder, and the breaking energy was calculated by moving distance (cm) until the tire was broken and pushing force (kg). The average of the fracture energies at five equally spaced points on the circumference of one tire was taken as the fracture energy of each tire, and the result was evaluated by the impact fracture index determined by the following equation. (Impact fracture resistance index) = (Destruction energy of each tire) /
(Fracture energy of comparative example) x 100

The cord breakability is determined by assembling the test tire in a standard rim, filling the internal pressure of 725 kPa, and then mounting the tire on an actual vehicle.
After running on a rough road for 60,000 km, the tire was divided into six equal parts on the circumference, each part was dissected, and the number of cords broken in the third belt layer was measured.
It was indicated by an index when it was set to 100. The smaller the index is, the smaller the number of cord breaks is, and the more excellent the cord break resistance is.

Since the belt end separation resistance is governed by the crack length at the end of the belt ply, this crack length was used as an index of the belt end separation resistance. In other words, the test tires described above were incorporated into a standard rim, filled with an internal pressure of 725 kPa, and then mounted on an actual vehicle.Under a load corresponding to the maximum load capacity, a general road was run 100,000 km,
Thereafter, the tire was dissected, and the crack length at the end of the third belt layer of the belt was measured. The result was indicated by an index when the crack length in Comparative Example was 100. The smaller the index is, the smaller the crack length is, indicating that the belt end separation resistance is excellent.

The drawability was measured by measuring the number of breaks occurring during the drawing of the filament, as in Example 1, and expressed as an index when the value of Comparative Example was set to 100. The smaller the index, the smaller the number of times of disconnection, indicating that the wire drawing is more excellent.

[0036]

[Table 3]

[0037]

[Table 4]

From the comparison between the invention example and the comparative example in Tables 3 and 4, it can be seen that the belt made of a filament cord having a breaking elongation of 3.5% or more according to the present invention particularly improves the resistance to impact. In a conventional steel cord, the elongation at break of the filament was about 1.3 to 1.9%.
By subjecting the same filaments that compose the conventional steel cord to a bluing treatment, the breaking elongation was significantly increased to 3.5% or more. Invention Example 3
And 9 are examples of a filament diameter of 0.13 mm, Invention Examples 4 and 10 are examples of a filament diameter of 0.44 mm, Invention Examples 5 and
11 is an example having a carbon content of 0.50 wt%, and Invention Example 6 and
12 is an example in which the carbon content is 1.10 wt%.

Embodiment 3 A carcass 2 extending in a toroidal shape between a pair of bead cores 1 shown in FIG. A steel cord is applied to the belt 3 of the radial tire for construction vehicles comprising the six layers of the belt 3 arranged at an angle and the tread 4 arranged in the tire radial direction outside of the belt 3 to prototype a tire of size 37.00 R57. did. As the steel cord, a 3 + 9 + 15 + 1 structure shown in FIG. 6A and a 7 × 7 + 1 structure shown in FIG. 6B were adopted. In addition, the belt 3 has a steel cord on the carcass 2 in order from a radially outer side with respect to the equatorial plane of the tire, as first, second, and third steel cords.
In the case of 3, 5, and 6 belt layers, the first to fourth belts
20 °, the fifth to sixth belt layers are oriented in a direction inclined at an angle of 25 °, and the cords between the layers of the first to sixth belts are arranged so as to intersect. Code 3
The structure was a + 9 + 15 + 1 structure or a 7 × 7 + 1 structure, and the remaining two layers had a 4 × 6 structure. The specifications of the cords of the first to fourth belts are shown in Tables 5 and 6, and the other belt cords were conventional steel cords.

The tires thus obtained were examined for impact resistance, cord breakage in carcass ply, ply end separation, and wire drawing. The results of these surveys are shown in Tables 5 and 6.
The evaluation results are shown based on the comparative examples in each table.

Here, since the impact fracture resistance has a correlation with the plunger energy, it is preferable to use the plunger energy as an index, but it is difficult to measure the plunger energy with a construction vehicle tire. Therefore, regarding the impact fracture resistance, a 10.00 R20 14PR radial tire for trucks and buses having a one-ply carcass and a six-layer belt is shown in FIG. 7 (a).
The + 9 + 15 + 1 structure and the 7 × 7 + 1 structure shown in FIG. Then, the test tire was mounted on a standard rim, filled with an internal pressure of 725 kPa, and left at room temperature for 3 hours or more. After that, the tire was attached to the testing machine, the tip of the plunger (diameter: 38 mmφ) was matched with the center of the tread of the tire, and the air pressure (240 Pa) was checked.
The plunger is pushed into the tire at a load speed of 50 ± 2.5 mm / min, and the movement of the plunger and the measurement of the pushing force are recorded on an XY recorder. cm) x pushing force (kg)
Was calculated. The average of the fracture energies at five points on the circumference of one tire was taken as the fracture energy of each tire, and the result was evaluated by the impact fracture index calculated by the following equation. (Impact fracture resistance index) = (Destruction energy of each tire) /
(Fracture energy of comparative example) x 100

The cord breakability is determined by assembling the test tire into a standard rim, filling the internal pressure of 500 kPa, mounting the tire on an actual vehicle and running it for 50,000 km, and then dissecting the tire to dissect the inner layer of the outermost layer of the belt. The number of broken cords was measured, and the result was indicated by an index when the measured value of the comparative example was set to 100. The smaller the index is, the smaller the number of cord breaks is, and the more excellent the cord break resistance is.

Since the belt end separation resistance is governed by the crack length at the end of the belt ply, this crack length was used as an index of the belt end separation resistance. In other words, the test tires described above were assembled into a standard rim, filled with an internal pressure of 500 kPa, and then mounted on an actual vehicle. Then, the crack length at the end of the innermost layer of the outermost layer of the belt was measured, and was indicated by an index when the crack length in Comparative Example was set to 100. The smaller the index is, the smaller the crack length is, indicating that the belt end separation resistance is excellent.

The wire drawing workability was measured in the same manner as in Example 1 by measuring the number of disconnections that occurred during the drawing of the filament, and expressed as an index when the value of the comparative example was set to 100. The smaller the index, the smaller the number of times of disconnection, indicating that the wire drawing is more excellent.

[0045]

[Table 5]

[0046]

[Table 6]

From the comparison between the invention examples and the comparative examples in Tables 5 and 6, it can be seen that the belt made of a cord having a filament having a breaking elongation of 3.5% or more according to the present invention particularly improves the resistance to impact. In the conventional steel cord, the elongation at break of the filament was about 1.9%. However, in the present invention, the same filament as that of the conventional steel cord was subjected to a bluing treatment to thereby obtain a breaking elongation. The growth was significantly increased to 3.5% or more. Inventive Examples 3 and 9 are examples in which the filament diameter is 0.08 mm, and Inventive Examples 4 and 10
Is an example having a filament diameter of 0.44 mm, Invention Examples 5 and 11 are examples having a carbon content of 0.50 wt%, and Invention Examples 6 and 12 are examples having a carbon content of 1.10 wt%.

[0048]

According to the present invention, it is possible to advantageously improve the durability of a pneumatic radial tire, particularly the durability against impact destruction of a belt ply.

[Brief description of the drawings]

FIG. 1 is a diagram showing a structure of a tire for a passenger car according to the present invention.

FIG. 2 is a diagram illustrating a cord structure applied to a tire for a passenger car.

FIG. 3 is a view showing a structure of a truck / bus tire according to the present invention.

FIG. 4 is a diagram exemplifying a cord structure applied to a truck / bus tire.

FIG. 5 is a diagram showing a structure of a construction vehicle tire according to the present invention.

FIG. 6 is a diagram showing an example of a multiple twist structure.

[Explanation of symbols]

 1 bead core 2 carcass 3 belt 4 tread

Claims (5)

[Claims] 1. A pneumatic radial tire having a carcass composed of a ply of radially arranged cords extending in a toroidal shape between a pair of bead portions as a skeleton, and having at least two layers of belts radially outside a crown portion of the carcass. And at least one layer of the belt has an elongation at break of 3.5%
A pneumatic radial tire comprising a cord formed of a plurality of filaments including the above steel filament. 2. The pneumatic radial tire according to claim 1, wherein the steel filament has been subjected to a bluing treatment after drawing. 3. The pneumatic radial tire according to claim 1, wherein the carbon content of the steel filament is 0.6 to 1.0 wt%. 4. The pneumatic radial tire according to claim 1, wherein the diameter of the steel filament is 0.10 to 0.40 mm. 5. A plurality of filaments including steel filaments having a breaking elongation of 3.5% or more in at least two belt layers, wherein cords are arranged crosswise between belt layers according to claim 1, 2, 3 or 4. A pneumatic radial tire using a cord.