JP2001328407A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic radial tire capable of reducing weight of the tire and capable of reducing rolling resistance while excellently keeping various tire performance such as ride comfortableness and maneuvering stability by restraining end part separation and cord breaking of a belt. SOLUTION: A belt layer 3 is formed by being parallelly arranged in a planar shape at intervals between single tracks or bundles as metallic single tracks or metallic bundles parallelly arranged in the belt width direction without intertwising a single or plural metallic wires having a flat cross section. A cross-sectional shape of the metallic wires is desirably a track shape having a set of parallel straight lines and a set of mutually opposing circular arcs.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire which achieves a reduction in weight without impairing various performances of the tire, and more particularly to a pneumatic radial tire suitable as a radial tire for a passenger car.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for reducing the weight of tires in order to improve fuel efficiency of automobiles. As an effective means of reducing weight, steel cords for tire reinforcement belts have been reviewed, and new technologies have been disclosed for their structures and arrangements. For example, JP-A-11-
No. 91311 discloses a technique in which a single metal wire is spirally formed in advance and a belt cord having a large attenuation is used, and it is described that the tire can be reduced in weight and riding comfort can be prevented from lowering. Also, in JP-A-10-292275,
A reinforcing belt was proposed in which several metal monofilaments were buried in rubber as a bundle aligned in the width direction without twisting, and it was described that rolling resistance and riding comfort were improved and belt edge separation was also suppressed. I have.

However, it has been found that the above-mentioned prior art has the following problems. That is, in the spirally shaped belt cord of JP-A-11-91311, since the diameter of the metal wire is large, a large strain is generated on the surface of the metal wire when bending deformation is repeatedly applied during traveling, and the There is a disadvantage that the metal wire is easily broken when a large bending deformation is applied during road running.

Further, in a reinforcing belt made of a metal wire bundle aligned in the width direction of Japanese Patent Application Laid-Open No. Hei 10-292275,
Although the separation at the belt end has been improved, the problem of insufficient bending stiffness of the belt still remains and needs to be improved.

[0005]

Therefore, in order to meet the need for further weight reduction of tires, we have used metal wires having a special cross-sectional shape as single wires or aligned bundles for tire reinforcement belts. Another object of the present invention is to solve the above-mentioned problems of tire performance such as breaking of a metal wire, peeling at a belt end, deterioration of rolling resistance and deterioration of durability.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and as a result of intensive studies on the structure, material, and arrangement of a reinforcing belt using a metal wire, the present invention has been completed. Was.

That is, the pneumatic radial tire of the present invention
A carcass layer comprising at least one radial carcass ply straddling in a toroidal manner between a pair of bead cores, and a tread layer disposed outside the crown region of the carcass layer in the tire radial direction to form a ground contact portion And a belt layer comprising a belt ply that forms a reinforcing portion disposed between the tread layer and the crown region of the carcass layer, wherein at least one belt of the belt layer is provided. The ply has a belt width without twisting one or more flat metal wires that are long in the belt ply width direction when at least most of the metal wires in the belt ply are viewed in a cross section orthogonal to the longitudinal direction. Exists as a single metal wire or metal wire bundle aligned in parallel in the direction, and the metal single wire or metal wire bundle is It is characterized in that the belt layer is formed by being arranged in parallel in the belt width direction at an interval and buried in rubber.

Here, the belt layer is composed of two belt plies, and all belt plies of the belt layer are
At least most of the metal wires in the belt ply were aligned in parallel without twisting one or more flat metal wires long in the width direction of the belt ply when viewed in a cross section orthogonal to the longitudinal direction. It is advantageous that the metal single wire or the metal wire bundle is formed as a single metal wire or a metal wire bundle, and the metal single wire or the metal wire bundle is formed in parallel and two-dimensionally arranged at intervals between the single wires or bundles in the width direction of the belt layer. is there.

[0009] The ratio of the short diameter D _S to major D _L of the metal wire bundle in a cross section perpendicular to the longitudinal direction of the metal wire bundle D
_{When S} / D _L is d _L , the short diameter is d _S , and the number of metal wires in the bundle is n, the length of the metal wire in a cross section orthogonal to the longitudinal direction of the metal wire is approximately d _S / (n × d _L ).

The number n of metal wires in the metal wire bundle is n
But it from two is four, minor axis of the cross section perpendicular to the longitudinal direction of the metal wire is a 0.15～0.30Mm, diameter d _L to the minor axis d _S ratio of d _L / d It is preferable that _S is in the range of 2.0 to 4.0.

The tensile strength of the metal wire is 3130-4.
Advantageously, it is 410 MPa, and the material of the metal wire is a steel material containing at least 0.7% by weight of carbon.

The belt layer is composed of two belt plies including a bundle of metal wires, the total thickness of the two belt plies is G ₁ , and the thickness of the metal wires of the radial inner belt ply and the outer belt ply is two. Assuming that the interval between them is G ₂ and the interval between the metal wire bundles in each belt ply is δG, the following equation is satisfied: 1.00 mm ≦ G ₁ ≦ 2.00 mm (1) 0.32 mm ≦ G ₂ ≦ 0.65 mm (2) It is preferable that 0.35 mm ≦ δG ≦ 1.00 mm (3) is satisfied, and the angle between the metal wire and the equatorial plane of the tire is 15 to 35 °.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A pneumatic radial tire according to one embodiment of the present invention will be specifically described with reference to FIGS.

The pneumatic radial tire of the present invention has a carcass layer 2 composed of at least one radial carcass ply straddling in a toroidal manner between a pair of bead cores 1 and a tire diameter in a crown region of the carcass layer. And a belt ply (here, 2) that is disposed between the tread layer and the crown region of the carcass layer and forms a reinforcing portion.
And a belt layer 3 composed of 3a and 3b).

[0015] At least one belt ply of the belt layer has a flat shape or a shape in which at least most of the metal wires in the belt ply are long in the width direction of the belt ply when viewed in a cross section orthogonal to the longitudinal direction. It exists as a metal single wire or metal wire bundle in which a plurality of metal wires are aligned in parallel in the belt width direction without twisting, and the metal single wire or metal wire bundle is spaced apart between single wires or bundles in the belt width direction and parallel. The belt layer is formed by being arranged in the belt width direction in a plane and embedded in rubber.

Conventionally, the metal wire used for the belt layer to reinforce the circumferential rigidity of the tire has a substantially circular cross section perpendicular to the length direction, as shown in FIGS. However, the metal wire used in the belt layer of the present invention is characterized in that its cross section is flat as shown in FIGS. When compared with the same cross-sectional area, the flat-shaped metal wire has substantially the same tensile elastic modulus in the length direction as the circular-shaped metal wire, but the bending elastic modulus during bending deformation in the short diameter plane is smaller. The distortion generated on the surface is small. Therefore, the belt layer of the present invention using flat metal wires arranged with their major diameters parallel to the tire belt layer as shown in FIGS. 6 and 7 has sufficient circumferential rigidity as a reinforcing belt. Since the surface distortion is small during repeated bending deformation while holding, a belt with good durability that does not easily cause line breakage is obtained. Other advantages of using flat cross-section metal wires include a larger cross-sectional area, which can improve the productivity of wire drawing, improve the efficiency of treating the treated material, reduce the surface irregularities of the cord, and enhance the belt pulling rigidity. And help to improve the steering stability.

Among the flat metal wires, those having a track shape having a cross-sectional shape having a set of parallel straight lines and a set of mutually facing arcs as shown in FIGS. There are advantages. That is, since it is straight in the width direction of the belt layer, the outer shape of the belt ply has less irregularities, and the shear force acting on the interlayer rubber effectively acts,
The tensile rigidity of the belt layer is enhanced, and the steering stability of the tire can be improved.

In the present invention, among the metal wires having a flat cross section, typically, a single metal wire or a metal bundle in which a steel cord is arranged in parallel in the belt width direction without twisting one or more metal wires. The metal single wires or metal wire bundles are arranged in parallel in the belt width direction at intervals between the single wires or bundles in the belt width direction to form a belt layer. Here, at least most or all of the metal wires are used as a metal wire bundle in which two to four metal wires are arranged in parallel in the belt width direction without twisting, and this metal wire bundle is interposed between the single wires in the belt width direction. Alternatively, it is most preferable to form a belt layer by arranging the belt layers in parallel in the belt width direction with an interval between the bundles. Particularly for pneumatic radial tires for passenger cars, the above-mentioned belt layer is
It is preferred to be composed of layers.

The preferred number of metal wires in the metal wire bundle is 2 to
When the number of wires is four, the spacing between the metal wires becomes narrower with one wire, and the effect of suppressing the belt peeling is reduced. On the other hand, when the number is five or more, the processing speed in the process of manufacturing the treat material is slow, This is because it is difficult to perform a processing operation for aligning in a plane.

When the belt layer is applied to a tire, all the layers of the belt layer are arranged in parallel without twisting one or more metal wires in which at least most of the metal wires in the layer have a flat cross section. Exist as aligned metal single wires or metal wire bundles, and the metal single wires or metal wire bundles are arranged in a plane in parallel at intervals between single wires or bundles in the belt layer width direction to form a belt layer. Is most advantageous.

The short diameter of the flat metal wire is 0.15 to 0.30.
mm. If the minor axis is less than 0.15 mm, the rigidity of the belt layer is insufficient, and the steering stability of the tire is impaired. If the minor axis exceeds 0.30 mm, the surface distortion of the metal wire during large bending deformation increases, and the metal wire is likely to be broken when the vehicle turns sharply. The preferred range of the ratio of the major axis and the minor axis of the flat metal wire d _L / d _S, 2.0~4.0
The reason is that if it is less than 2.0, the above-mentioned effect is weakened, while the rolling of a metal wire having a high oblateness exceeding 4.0 tends to cause cracking of the metal wire.

The tensile strength of the metal wire of the present invention is 3130 to
4410 MPa is preferred. At less than 3130 MPa,
In order to secure the belt layer strength, the amount of use increases, which is disadvantageous in reducing the weight of the tire. Alternatively, the number of driving wires must be increased, the distance between adjacent metal wires becomes narrow, and the occurrence and propagation of peeling at the belt layer end cannot be suppressed. A metal wire having a tensile strength exceeding 4410 MPa is difficult to manufacture and is not suitable for mass production.

In order to obtain a high tensile strength, it is advantageous for the metal wire used in the present invention to contain at least 0.7% by weight of carbon, preferably at least 0.8% by weight of carbon. is there.

In the present invention, by using a single flat metal wire bundle or a metal wire bundle arranged in parallel in a plane for the belt layer, the total thickness of the belt layer can be reduced and the amount of rubber coated can be reduced. Weight can be reduced.

In the present invention, it is preferable that the belt layer has two layers. In this case, the total thickness of the covering rubber for embedding the two layers of metal wires is G ₁ , and the distance between the metal wires of the inner and outer layers in the radial direction is G. G ₂ , when the interval between the metal wire bundles in each layer is δG, the relationship of the following equation is 1.00 mm ≦ G ₁ ≦ 2.00 mm (1) 0.32 mm ≦ G ₂ ≦ 0.65 mm (2) 0.35 mm It is advantageous for implementation to satisfy ≦ δG ≦ 1.00 mm (3). If G ₁ is less than 1.00 mm, the treat is weak and molding of the tire is difficult, and if it exceeds 2.00 mm, the weight of the belt layer increases and the advantage of weight reduction is lost. G ₂ is 0.32m
If it is less than m, the belt layer is likely to be deformed by the input to the tire tread, and the durability is reduced. On the other hand, if it exceeds 0.65 mm, the tensile rigidity of the belt layer constituent member is reduced, so that the steering stability is deteriorated and the advantage of weight reduction is lost. δG
If it is less than 0.35 mm, the occurrence and propagation of peeling at the end of the belt layer cannot be prevented. On the other hand, if it exceeds 1.00 mm, the belt stiffness will decrease and the penetration resistance when a nail or the like is stepped on (penetration) ) Gets worse.

The organic fibers which are oriented substantially in the tire circumferential direction so as to cover the entire width thereof on the outer side in the radial direction of the above-mentioned belt layer of the present invention or to cover the vicinity of both ends thereof. By providing the cap layer layer made of, various tire performances can be further improved.

In the method of manufacturing a flat metal wire according to the present invention, the conventional equipment and processes for manufacturing a metal wire having a normal circular cross section are used as they are, and a roller is formed in the latter half of the wire drawing process. It can be made economically and simply by rolling with a die or passing through a flat-hole die.

[0028]

Embodiments of the present invention will be described below with reference to the drawings and tables. The tire of this embodiment is a pneumatic radial tire (size 175 / 70R14) having the structure shown in FIG.
In accordance with the specifications shown in the code specification column of Table 1,
It was produced by applying a belt layer composed of a first belt ply 3a inclined at an angle of 20 ° to the right and a second belt ply 3b inclined at an angle of 20 ° to the left on the equatorial plane of the tire.

Comparative Examples 1 and 2 show a conventional circular metal cross section.
In Comparative Example 1, the metal wire shown in FIG.
The comparative example 2 is a bundle of six metal wires. Implementation
In Examples 1 to 8, a flat track-shaped metal wire was used.
Only Example 1 is a uniform driving, and the remaining Examples 2 to 8
Number of bundles, wire diameter, rubber gauge, wire bundle
The distance between them is shown in Table 1. Example 1 uses d_L
/ D_SThe uniformity of a single metal wire with a track-shaped cross section of 4.0
By driving, δG is wider than in Conventional Example 1.
Example 2 uses d_L/ D_SHas a track-shaped cross section of 3.0
An array of two bundles of genus wires widens δG. Example 3
5 is d_L/ D_SIs 2.0 and the number of bundles is 3
These are four examples. In the sixth embodiment, δG is slightly narrower.
Example 7 has a minor axis d. _SIn Example 8, the six bundles and the bundle
This is an example in which the number of lines is increased.

A performance test was performed for each tire, and the results are shown in the lower part of Table 1 as indices relative to the performance of Comparative Example 2 as 100.

[0031]

[Table 1]

The tire of Example 1 has a major axis / minor axis ratio d _L /
A flat track-shaped metal wire with d _S of 4.0 was uniformly driven, and δG was wider than that of Comparative Example 1.
The belt edge peeling resistance is improved. Example 2, in which the major diameter / minor diameter ratio d _L / d _S is an array of metal wires of the track shape of 3.0 by two beams, while minor d _S is the same as the Comparative Example 2, in flat shape As a result, δG is increased, and the belt edge peeling resistance is further improved. In addition, unevenness of the outer shape of the metal wire bundle is eliminated, and steering stability is further improved. Examples 3-5, d _L / d _S is respectively three bundles of metal wires of the track shape of 2.0, two bundles, which was arranged in four bundles, and excellent resistance to belt edge peelable I have. In Example 6, δ
Although G is a narrow example, the belt edge peeling resistance is slightly lower. Example 7 is an example in which the minor diameter d _S is slightly larger, but the belt breaking resistance is slightly inferior. Example 8 is an example in which the number of bundles is large, and there is no particular problem with the tire performance, but the rolling (calender) workability is slightly inferior.

Hereinafter, the test method performed in this example will be described in detail.

<Belt end peeling test> The test tire was assembled on a regular rim, filled with an internal pressure of 1.5 kgf / cm ² , mounted on a test car, and allowed to travel on a general road for 60,000 km. The tire is dissected to measure the length of the crack formed at the edge of the belt. The reciprocal of the crack length of each test tire was calculated and is shown as an index with the reciprocal value of the conventional tire being 100. The larger the index, the better the belt edge separation resistance.

<Ride comfort test> A predetermined load is applied to a tire test iron drum having a diameter of 2 m and a protrusion of 2 cm in width and 1 cm in height attached thereto, and the test tire is pressed to rotate the drum. The vibration waveform in the vertical load direction when the tire rides over the protrusion on the drum is measured by an accelerometer, and the reciprocal of the amplitude of the first cycle is obtained. The larger the index, the better the ride quality.

<Driving stability test> JIS standard D4202
The test tire adjusted according to the above was installed on a drum testing machine having an outer diameter of 3 m, a load determined from a predetermined size and an internal pressure was applied, and the tire was preliminarily run at a speed of 30 km / h for 30 minutes.
In order to eliminate the effect of the increase in internal pressure due to temperature rise, readjust the internal pressure to the specified value without the load, and then again adjust the slip angle from ± 1 ° to ± 4 ° at the same speed and load under the same load, every 1 degree Cornering force (CF) per unit angle at each of the positive and negative angles was measured continuously, and their average was calculated to determine the cornering power (CP). The CP of each test tire is divided by the CP of the conventional tire and displayed as an index. The larger the index, the better the steering stability.

<Rolling Resistance> The rolling resistance was measured by using SA
EJ1269, and the conventional tires
As an index. The higher the index, the lower the rolling resistance.

<Belt Breaking Test> In this test, the test tire was mounted on an actual vehicle, and after traveling 20,000 km at a speed of 60 km / h on a curved road, the tire was dissected, and the test tire was dissected. Reinforcing members (wire bundles or cords) were sampled, the number of the reinforcing members in a broken state was investigated, and the reciprocal thereof was indicated as an index with the conventional tire as 100. The higher the index, the better the belt refraction resistance.

<Rolling workability test> Preparation of cord and rolling (calender) before combining cord and rubber
The time required for work was measured, and compared with the work time of the conventional code, (ほ ぼ) indicates that the time was almost the same, (△) indicates the time increase within 20%, and (x) indicates the time increase more than that. .

[0040]

As described above, according to the pneumatic radial tire according to the present invention, there are various problems due to weight reduction, namely, peeling resistance at the end of the belt, riding comfort, steering stability, and belt resistance. It was found that the tire was a lightweight pneumatic radial tire having improved rolling resistance and other properties and excellent rolling resistance.

[Brief description of the drawings]

FIG. 1 is a sectional view of a pneumatic radial tire according to the present invention.

FIG. 2 is an example of a bundle of two metal wires according to the present invention.

FIG. 3 is a conventional example of three bundles of metal wires having a circular cross section.

FIG. 4 is a conventional example in which metal wires having a circular cross section are arranged at equal intervals.

FIG. 5 is a conventional example in which metal wires are twisted into a 1 × 3 structure.

FIG. 6 is an example of a bundle of three metal wires according to the present invention.

FIG. 7 is a view in which two layers in which two bundles of metal wires according to the present invention are covered with rubber are overlapped in a longitudinal sectional view.

[Explanation of symbols]

1 bead core 2 minor G ₁ 2-layer carcass ply 3 the belt layer 3a first belt ply 3b second belt ply 4 major diameter d _S metal wire minor d _L metal wire diameter D _S metal wire bundle of tread D _L metal wire bundle Total thickness of belt ply (mm) G ₂ Distance between metal wires of two-layer belt ply (mm) δG Distance between metal wire bundles in layer (mm) R ₁ First layer coating rubber R ₂ Second layer coating Rubber

Claims (11)

[Claims] 1. A carcass layer comprising at least one radial carcass ply straddling in a toroidal manner between a pair of bead cores, and a ground contact portion disposed outside a crown region of the carcass layer in a tire radial direction. A pneumatic radial tire, comprising: a tread layer that forms a belt layer; and a belt layer that is disposed between the tread layer and the crown region of the carcass layer and that includes a belt ply that forms a reinforcing portion. At least one belt ply is formed by twisting one or more flat-shaped metal wires that are long in the width direction of the belt ply when at least most of the metal wires in the belt ply are viewed in a cross section orthogonal to the longitudinal direction. Exists as a single metal wire or a bundle of metal wires aligned in parallel in the belt width direction without being aligned, and the single metal wire or the bundle of metal wires is simply aligned in the belt width direction. A pneumatic radial tire characterized by spaced apart across or between bundles are arranged in a planar manner the belt width direction in parallel are embedded in the rubber belt layer is formed. 2. The pneumatic radial tire according to claim 1, wherein the belt layer comprises two belt plies. 3. The method according to claim 1, wherein all belt plies of the belt layer are:
At least most of the metal wires in the belt ply were aligned in parallel without twisting one or more flat metal wires long in the width direction of the belt ply when viewed in a cross section orthogonal to the longitudinal direction. The metal single wire or the metal wire bundle is present as a metal single wire or a metal wire bundle, and the metal single wire or the metal wire bundle is formed in parallel and two-dimensionally arranged at intervals between single wires or bundles in the width direction of the belt layer. Pneumatic radial tire. Wherein the ratio of the short diameter D _S to major D _L of the metal wire bundle in a cross section perpendicular to the longitudinal direction of the metal wire bundle D _S /
D _L is d _L , the short diameter is d _S , and the number of metal wires in the bundle is n, in the cross section orthogonal to the longitudinal direction of the metal wire.
Wherein d is approximately d _S / (n × d _L ).
The pneumatic radial tire according to any one of the above. 5. The metal wire according to claim 1, wherein the cross-sectional shape of the metal wire is a track shape having a set of parallel straight lines and a set of arcs facing each other and projecting outward. Pneumatic radial tire. 6. The number n of metal wires in the metal wire bundle is 2
The pneumatic radial tire according to any one of claims 1 to 5, wherein the number is from four. 7. A minor axis of the cross section perpendicular to the longitudinal direction of the metal wire is a 0.15～0.30Mm, the ratio d _L / d _S of the long diameter d _L to the minor axis d _S 2.0 The pneumatic radial tire according to any one of claims 1 to 6, wherein the range is from 4.0 to 4.0. 8. The metal wire having a tensile strength of 3130 to 441.
The pneumatic radial tire according to any one of claims 1 to 7, wherein the pressure is 0 MPa. 9. The material of the metal wire is at least 0.7
The pneumatic radial tire according to any one of claims 1 to 8, wherein the pneumatic radial tire is a steel material containing carbon by weight. 10. The belt layer is composed of two belt plies including a bundle of metal wires, the total thickness of the two belt plies is G ₁ , and the total thickness of the metal wires of the radial inner belt ply and the outer belt ply is defined as G ₁ . Assuming that the interval between them is G ₂ and the interval between the metal wire bundles in each belt ply is δG, the following equation is satisfied: 1.00 mm ≦ G ₁ ≦ 2.00 mm (1) 0.32 mm ≦ G ₂ ≦ 0.65 mm (2) The pneumatic radial tire according to any one of claims 1 to 9, which satisfies 0.35 mm ≤ δG ≤ 1.00 mm (3). 11. The angle between the metal wire in the belt layer and the equatorial plane of the tire is 15 to 35 °.
The pneumatic radial tire according to any one of the above items.