JP2001206016A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic radial tire with reduced weight and suppressed noise. SOLUTION: This pneumatic radial tire 10 is formed by laminating an inclined belt layer 20A composed of a steel cord and a circumferential belt layer 20B composed of a organic fiber cord so as to reduce the weight compared with a cross belt structure formed by laminating two inclined belt layers composed of steel cord together. Because this has only one inclined belt layer 20A, the bending rigidity in the tire width direction is reduced compared with that of the cross belt structure. As a result, the wall face in the circumferential main groove 24 is vibrated so as to vibrate the air in its inside. The cross section of the circumferential main groove 24 is thus set to 125 mm2 or more so as to suppress air column resonance and suppress the noise.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly to a pneumatic radial tire having excellent cornering properties and excellent high-speed durability. Regarding tires.

[0002]

2. Description of the Related Art In order to provide a pneumatic radial tire having excellent circumferential stiffness and in-plane bending stiffness, two belt layers conventionally formed of a steel cord are laminated on a crown portion, and one belt is provided. A cross belt structure in which the cord of the layer and the cord of the other belt layer are inclined in opposite directions with respect to the tire equatorial plane is widely used.

[0003] However, in recent years, energy saving has been called for, and also in automobiles, fuel efficiency has been improved by reducing the weight. Along with this, the demand for lighter tires also tends to increase year by year, and this tendency is particularly remarkable in general-purpose pneumatic radial tires for passenger cars.

In order to reduce the weight, an inclined belt including a plurality of steel cords inclined with respect to the tire equatorial plane and a peripheral belt including a plurality of organic fiber cords or steel cords parallel to the tire equatorial plane are provided. A pneumatic radial tire including a directional belt has been proposed (for example, Japanese Patent Application Laid-Open No. 8-318706).

[0005] In a pneumatic radial tire described in JP-A-8-318706 (hereinafter referred to as "prior art"),
The belt has two layers, and the use of a high-strength organic fiber cord (or an optimally arranged steel cord) for the circumferential belt reduces the weight and improves high-speed durability.

[0006]

However, in the above prior art, the bending rigidity in the tire width direction is lower than that in the cross belt structure in which two inclined belt layers are stacked. Due to the decrease in the bending rigidity in the tire width direction, it becomes easier to excite the air in the circumferential groove formed in the tread, and noise due to air column resonance increases.

[0007] Therefore, when the above structure is employed for weight reduction, it is necessary to suppress noise due to columnar resonance.

In view of the above, an object of the present invention is to provide a pneumatic radial tire which is reduced in weight while suppressing noise.

[0009]

In order to suppress columnar tube resonance, it is considered effective to change the cross-sectional shape, specifically, the cross-sectional area. Therefore, a test tire having a circumferential main groove formed at the center in the tire width direction is mounted on a drum, and a predetermined volume of sound (P1) is output from a speaker behind the ground contact surface under a state in which a predetermined load is applied. Then, by measuring the sound volume (P2) collected by a microphone disposed in front of the ground plane, the relationship between the columnar tube resonance (sound field characteristics P2 / P1) and the cross-sectional area of the main groove was examined. As a result, as shown in FIG.
The columnar resonance was maximized when the cross-sectional area of the main groove was about 80 mm ² , and it was confirmed that noise (air column resonance) could be suppressed by increasing or decreasing the cross-sectional area.
However, if the cross-sectional area is less than the current value (cross-sectional area of 65 mm ² ), there is a disadvantage that the drainage property is reduced and the wet performance is reduced. Therefore, it has been found that the columnar resonance can be further suppressed by increasing the cross-sectional area (the cross-sectional area is set to 125 mm ² or more).

[0010] According to the first aspect of the present invention, a plurality of cords or filaments extending obliquely with respect to the tire equatorial plane are provided on an outer periphery of a crown portion of a carcass that forms a toroid over at least a pair of bead cores. One arranged inclined belt layer, at least one circumferential belt layer located on the inclined belt layer, and having a plurality of cords arranged substantially parallel to a tire equatorial plane, and the circumferential belt In a pneumatic radial tire provided with a circumferential groove on a tread provided on the tire radial direction outside of the layer, a cross-sectional area of the circumferential groove on the tire equatorial plane side is 125 mm ² or more.

The operation of the pneumatic radial tire according to the first aspect will be described.

[0012] The pneumatic radial tire according to the present invention comprises:
It is composed of one inclined belt layer and at least one circumferential belt layer. For example, 1 including steel cord
A weight reduction as compared with a cross belt structure in which two inclined belt layers including a steel cord are laminated by comprising one inclined belt layer and one circumferential belt layer including a fiber cord. Can be.

However, since one of the belt layers is a circumferential belt layer, the flexural rigidity in the tire width direction is reduced, and the tread forming the wall surface of the circumferential groove is easily deformed. Excitation of air causes noise due to air column resonance.

Therefore, in the pneumatic radial tire according to the present invention, the cross-sectional area of the circumferential groove on the equatorial plane side (closest to the equatorial plane) that most contributes to noise generation is set to 125 mm ² or more. Thus, the air column resonance is suppressed to suppress noise.

According to a second aspect of the present invention, in the pneumatic radial tire according to the first aspect, the cord of the circumferential belt layer is made of polyethylene terephthalate fiber or nylon fiber, has a twin twist structure, and has a total denier. Number D
T is in the range of 1000d to 6000d, and assuming that the number of twists of this cord is T (number of times / 10 cm) and the specific gravity is ρ, the twisting coefficient Nt is Nt = T × (0.139 × DT /
It is characterized in that in the range of ^{3 ≦ 0.3 - 2 × 1 /} ρ) 1/2 × 10.

The operation of the pneumatic radial tire according to claim 2 will be described.

Sufficient cornering performance can be obtained by setting the cord of the circumferential belt layer to polyethylene terephthalate fiber or nylon fiber and setting the twist coefficient Nt of the cord to 0.3 or less.

The cord of the circumferential belt layer has a twin-twisted structure in view of improving the compression fatigue property of the cord itself and workability, and the total denier number DT is 1000d to 60d.
The reason for setting the range to 00d is that if it is less than 1000d, it is difficult to physically insert a code. On the other hand, 600
If it exceeds 0d, the cord becomes too thick, and the amount of rubber must be increased at the same time, resulting in an increase in tire weight.

On the other hand, if the twist coefficient Nt is too small, there is a possibility that the cords may be loosened and the workability may be deteriorated.
It is preferred to be 0.1 or more.

Further, by using a polyethylene terephthalate fiber or a nylon fiber for the cord of the circumferential belt layer, the cord breakage due to compression fatigue can be reduced to the conventionally used aramid fiber cord having a twist coefficient (Nt) of 0.3 or less. It is less likely to occur.

Here, the twin-twisted structure means one yarn or two yarns.
Twisted and twisted in a direction opposite to the twisting (upward twisting).

The total denier number DT means the product of the original yarn denier and the number of twists.

According to a third aspect of the present invention, in the pneumatic radial tire according to the first aspect, the cord of the circumferential belt layer is made of polyethylene naphthalate fiber, has a twin twist structure, and has a total denier number DT. Is 1000d-60
When the number of twists of this cord is T (number of times / 10 cm) and the specific gravity is ρ, the twist coefficient Nt is N
t = T × (0.139 × DT / 2 × 1 / ρ) ^1/2 × 10
^-3 ≦ 0.6.

The operation of the pneumatic radial tire according to claim 3 will be described.

The cord of the circumferential belt layer is made of polyethylene naphthalate fiber, and the twist coefficient Nt of this cord is set to 0.1.
By setting it to 6 or less, sufficient cornering performance can be obtained.

The reason why the cord of the circumferential belt layer has a twin-twist structure is to improve the compression fatigue property of the cord itself and the workability, and the total denier number DT is 1000d to 60d.
The reason for setting the range to 00d is that if it is less than 1000d, it is difficult to physically insert a code. On the other hand, 600
If it exceeds 0d, the cord becomes too thick, and the amount of rubber must be increased at the same time, resulting in an increase in tire weight.

On the other hand, if the twist coefficient Nt is too small, the cords may be loosened and the workability may be deteriorated.
It is preferred to be 0.1 or more.

Further, by using polyethylene naphthalate fiber for the cord of the circumferential belt layer, the cord breakage due to compression fatigue can be prevented by the twist factor (Nt) conventionally used.
Is less likely to occur as compared with an aramid fiber cord of 0.3 or less.

According to a fourth aspect of the present invention, in the pneumatic radial tire according to the first aspect, the cord of the circumferential belt layer is made of vinylon fiber and has a twin twist structure,
When the total denier number DT is in the range of 1000d to 6000d, and the number of twists of this cord is T (number of times / 10 cm) and the specific gravity is ρ, the twist coefficient Nt is Nt = T × (0.1
39 × DT / 2 × 1 / ρ) ^1/2 × 10 ⁻³ ≦ 0.6.

The operation of the pneumatic radial tire according to claim 4 will be described.

Sufficient cornering performance can be obtained by using vinylon fiber as the cord of the circumferential belt layer and setting the twist coefficient Nt of the cord to 0.6 or less.

The cord of the circumferential belt layer has a twin-twist structure from the viewpoint of improving the compression fatigue property of the cord itself and workability, and the total denier number DT is 1000d to 60d.
The reason for setting the range to 00d is that if it is less than 1000d, it is difficult to physically insert a code. On the other hand, 600
If it exceeds 0d, the cord becomes too thick, and the amount of rubber must be increased at the same time, resulting in an increase in tire weight.

On the other hand, if the twist coefficient Nt is too small, the cords may be loosened and the workability may be deteriorated.
It is preferred to be 0.1 or more.

Further, by using vinylon fiber for the cord of the circumferential belt layer, cord breakage due to compression fatigue can be prevented.
It is less likely to occur than a conventionally used aramid fiber cord having a twist coefficient (Nt) of 0.3 or less.

According to a fifth aspect of the present invention, in the pneumatic radial tire according to the first aspect, the cord of the circumferential belt layer is made of aramid fiber, has a twin-twist structure,
When the total denier number DT is in the range of 1000d to 6000d, and the number of twists of this cord is T (number of times / 10 cm) and the specific gravity is ρ, the twist coefficient Nt is Nt = T × (0.1
39 × DT / 2 × 1 / ρ) ^1/2 × 10 ⁻³ ≧ 0.3.

The operation of the pneumatic radial tire according to claim 5 will be described.

By setting the cord of the circumferential belt layer to aramid fiber and setting the twist coefficient Nt of the cord to 0.3 or more, good cord breakage resistance can be obtained.

The cord of the circumferential belt layer has a twin-twist structure in view of improving the compression fatigue property of the cord itself and workability, and the total denier number DT is 1000d to 60d.
The reason for setting the range to 00d is that if it is less than 1000d, it is difficult to physically insert a code. On the other hand, 600
If it exceeds 0d, the cord becomes too thick, and the amount of rubber must be increased at the same time, resulting in an increase in tire weight.

According to a sixth aspect of the present invention, there is provided the pneumatic radial tire according to any one of the first to fifth aspects, wherein a tangent loss tan δ of a cord of the circumferential belt layer is provided.
But initial tension 1kgf / piece, strain amplitude 0.1%, frequency 20H
z, being not more than 0.3 under the condition of an ambient temperature of 25 ° C.

The operation of the pneumatic radial tire according to claim 6 will be described.

The fibers of PET, nylon, PEN, vinylon and aramid have a large work loss and tend to generate heat. Therefore, in a high-speed durability test, these fiber cords may be melted. Therefore, by setting the tangent loss tan δ of the cord of the circumferential belt layer to 0.3 or less under the conditions of an initial tension of 1 kgf / strain, a strain amplitude of 0.1%, a frequency of 20 Hz, and an ambient temperature of 25 ° C. Melting of these fiber cords can be prevented.

According to a seventh aspect of the present invention, in the pneumatic radial tire according to the first aspect, the cord of the circumferential belt layer has an elastic modulus of 3000 kgf / mm ² or more,
It is a twisted steel cord.

The operation of the pneumatic radial tire according to claim 7 will be described.

When a steel cord is used as the cord of the circumferential belt layer, the above-mentioned P is applied to the circumferential belt by using a twisted structure having an elastic modulus of 3000 kgf / mm ² or more.
Compared to the case where an organic fiber cord such as ET, nylon, PEN, vinylon, or aramid is used, although the tire weight is slightly increased, the circumferential rigidity can be further increased, and sufficient cornering power can be obtained. .

When the elastic modulus is less than 3000 kgf / mm ² , the rigidity cannot be improved more effectively, and when the structure is not a twisted structure, the advantage of weight and cost is reduced. .

The number of steel cords to be driven is 15 per 50 mm from the viewpoint of securing rigidity in the circumferential direction and reducing the weight.
It is preferable that the number be within the range of 50 to 50.

According to an eighth aspect of the present invention, in the pneumatic radial tire according to any one of the first to seventh aspects, the elastic modulus of the rubber covering the circumferential belt layer is 200.
kgf / mm ² or more.

The operation of the pneumatic radial tire according to claim 8 will be described.

If the modulus of elasticity of the rubber covering the circumferential belt layer is too low, the cord tends to move easily, causing local buckling of the cord and possibly causing the cord to break. Therefore, by setting the elastic modulus of the coating rubber of the circumferential belt layer to 200 kgf / mm ² or more, it is possible to prevent the cord from being cut.

As shown in FIG. 7A, a steel jig having a cylindrical cavity having a diameter d of 14 mm and a height h of 28 mm, as shown in FIG. 10
0, the jig 100 is filled with a rubber test piece 102 without any gap as shown in FIG.
4 and 0.6 mm on the upper and lower surfaces of the rubber test piece 102.
The load W is applied at a speed of / min, the displacement at this time is measured by the laser displacement meter 106, and is calculated from the relationship between the load and the displacement.

According to a ninth aspect of the present invention, in the pneumatic radial tire according to any one of the first to eighth aspects, the cord of the circumferential belt layer is spirally wound. It is characterized by.

The operation of the pneumatic radial tire according to claim 9 will be described.

By spirally winding the cord of the circumferential belt layer, the uniformity of the tire can be improved.

According to a tenth aspect of the present invention, in the pneumatic radial tire according to any one of the first to ninth aspects, the cord or filament of the inclined belt layer is made of a steel material. I have.

The operation of the pneumatic radial tire according to claim 10 will be described.

By using a steel material for the cord or filament of the inclined belt layer, sufficient tire strength can be obtained.

According to an eleventh aspect of the present invention, in the pneumatic radial tire according to any one of the first to tenth aspects, the cord or filament of the inclined belt layer has an inclination angle of 15 degrees with respect to the tire equatorial plane. It is characterized in that it is in the range of 45 ° to 45 °.

The operation of the pneumatic radial tire according to the eleventh aspect will be described.

By setting the angle of inclination of the cord or filament of the inclined belt layer with respect to the tire equatorial plane in the range of 15 ° to 45 °, sufficient in-plane shear rigidity can be obtained in the tread.

The twelfth aspect of the present invention is the first aspect of the present invention.
2. The pneumatic radial tire according to claim 1, wherein a thickness (tl) of a rubber located between a cord or a filament of the inclined belt layer and a cord of the circumferential belt layer is determined by a cross-section in a tire width direction. Inside, it is characterized by being larger at the end in the tire width direction than at the center in the tire width direction.

The operation of the pneumatic radial tire according to claim 12 will be described.

The thickness (tl) of the rubber located between the cords or filaments of the inclined belt layer and the cords of the circumferential belt layer is determined at the tire width direction ends at the tire width direction center portion in the tire width direction cross section. It is larger than. Therefore, the tire bending rigidity in the circumferential direction is relatively lower at the center in the tire width direction than at the end in the tire width direction. As a result, the tire contact length is longer in the center region of the tread and shorter in both shoulder regions, and the contact shape is a rounded shape with sharp corners. Therefore, when traveling on a wet road surface, water ahead in the tire traveling direction is quickly removed to the side of the tire, and the occurrence of hydroplaning can be suppressed.

According to a thirteenth aspect of the present invention, in the pneumatic radial tire according to the twelfth aspect, the thickness (t2) of the rubber located between the cord of the circumferential belt layer and the inner circumferential surface of the tread rubber is reduced. In the cross section in the tire width direction, the width is larger at the center portion in the tire width direction than at the end portion in the tire width direction.

The operation of the pneumatic radial tire according to claim 13 will be described.

The thickness (t2) of the rubber located between the cord of the circumferential belt layer and the inner circumferential surface of the tread rubber is larger at the center in the tire width direction than at the end in the tire width direction. . As a result, in the pneumatic radial tire according to claim 15, the sum of the thickness of the inclined belt layer and the thickness of the circumferential belt layer is constant. Therefore, it is possible to prevent unevenness corresponding to the cord from appearing near the center of the tire inner peripheral surface in the tire width direction after tire vulcanization (cord appearance phenomenon).

The invention according to claim 14 is the invention according to claims 1 to 1
3. The pneumatic radial tire according to claim 1, wherein the circumferential belt layer has at least two layers at a central portion in a tire width direction.

The operation of the pneumatic radial tire according to claim 14 will be described.

By making the circumferential belt layer at least two layers at the central portion in the tire width direction, the protrusion at the central portion in the tire width direction during high-speed running can be further suppressed.

The invention according to claim 15 provides the invention according to claims 1 to 1
5. The pneumatic radial tire according to claim 4, wherein the circumferential belt layer has at least two layers at an end portion in a tire width direction.

The operation of the pneumatic radial tire according to claim 15 will be described.

By forming the circumferential belt layer into two layers at least at the end in the tire width direction, the belt end separation can be further suppressed.

[0072]

Next, an embodiment of the radial tire of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the radial tire 10 has a carcass 14 which is folded back from the tire inside to the outside around a bead core 12 embedded in a bead portion 11,
Tread portion 16 located at the crown of carcass 14
And a sidewall portion 18 located on a side portion of the carcass 14, and two belt layers 20 disposed inside the tread portion 16.

The carcass 14 has fiber cords arranged in a direction substantially perpendicular to the circumferential direction. In the present embodiment, the carcass 14 is composed of one carcass ply.

As shown in FIG. 2, the belt layer 20 includes a single inclined belt layer 20A in which a plurality of steel cords 19 extending inclining with respect to the tire equatorial plane CL are arranged, and a belt layer 20A on the inclined belt layer 20A. And a circumferential belt layer 20B in which a plurality of organic fiber cords 21 are arranged substantially parallel to the tire equatorial plane CL.

Here, the inclination angle θ1 of the steel cord 19 of the inclined belt layer 20A with respect to the tire equatorial plane CL is 1
The angle is preferably in the range of 5 ° to 45 °.

On the other hand, the circumferential belt layer 20B is a rubber-pulled narrow strip including a plurality of organic fiber cords 21 (or one in some cases). It is wound endlessly in a spiral shape (spiral shape) so as to be parallel (0 ° to 5 °).

The organic fiber cords of the circumferential belt layer 20B are polyethylene terephthalate fiber (PET), nylon fiber, polyethylene naphthalate fiber (PEN, preferably polyethylene-2,6-naphthalate fiber), vinylon fiber, aramid fiber and the like. Are preferred, and a twin-twisted structure is preferred.
It is preferably in the range of 6000d.

Further, when the organic fiber cord of the circumferential belt layer 20B is polyethylene terephthalate fiber (PET) or nylon fiber, the twist coefficient Nt is 0.3 or less, and when the organic fiber cord is polyethylene naphthalate fiber (PEN) or vinylon fiber, it is twisted. Preferably, the coefficient Nt is 0.6 or less, and in the case of aramid fiber, the twist coefficient Nt is 0.3 or more.

The organic fiber cord of the circumferential belt layer 20B is made of polyethylene terephthalate fiber (PET), nylon fiber, polyethylene naphthalate fiber (PE).
N), in the case of vinylon fiber, the twist coefficient Nt is preferably set to 0.1 or more.

Further, the tangent loss tan δ of the organic fiber cord of the circumferential belt layer 20B is 0.3 or less under the conditions of an initial tension of 1 kgf / line, a strain amplitude of 0.1%, a frequency of 20 Hz, and an ambient temperature of 25 ° C. It is preferred that

Further, a steel cord can be used for the circumferential belt layer 20B instead of the organic fiber cord. In this case, the elastic modulus of the steel cord is 3000 kgf /
mm ² or more, preferably a twisted structure.

Further, the number of steel cords to be driven is
From the viewpoint of weight reduction, it is preferable to set the range of 15 to 50 pieces per 50 mm.

The elastic modulus of the rubber covering the circumferential belt layer 20B is preferably 200 kgf / mm ² or more.

In this embodiment, the circumferential belt layer 2
Although 0B is a single layer, at least the circumferential belt layer is formed at two layers in the central portion in the width direction, so that it is possible to further suppress the tire central portion from protruding during high-speed running. Further, by forming two circumferential belt layers at least at the width direction ends, belt separation can be reliably suppressed.

As shown in FIG. 3, on the surface of the tread portion 16, one circumferential main groove 24 (hereinafter, may be referred to as main groove 24) extending in the tire circumferential direction at the center in the tire width direction. And a plurality of inclined grooves 26 extending from the circumferential main groove 24 to both ends in the tire width direction, and a communication groove 28 connecting the adjacent inclined grooves 26 are formed.

Next, the operation of the pneumatic radial tire 10 of the present embodiment will be described.

The pneumatic radial tire 10 of the present embodiment
A circumferential belt layer 20B in which a plurality of organic fiber cords 21 are arranged substantially parallel to the tire equatorial plane CL.
Thereby, the circumferential rigidity of the tread portion 16 can be obtained, the internal pressure can be maintained, and high-speed durability can be obtained.

Further, the in-plane bending rigidity of the tread portion 16 is obtained by the inclined belt layer 20A in which a plurality of steel cords 19 extending obliquely with respect to the tire equatorial plane CL are arranged, and endure the lateral force during cornering. Can be.

However, since there is only one inclined belt layer 20A, the bending rigidity in the tire width direction is lower than that of a cross belt structure having two inclined belt layers. Therefore, the tread is likely to be deformed, and the wall surface of the circumferential main groove 24 formed in the tread portion 16 vibrates to excite the air in the main groove 24.

On the other hand, in the pneumatic radial tire 10 according to the present embodiment, since the cross-sectional area of the main groove 24 is 125 mm ² or more, air column resonance (sound field characteristics P2 / P1) is suppressed, and the noise level is reduced. (See FIG. 4).

The columnar resonance can also be reduced by reducing the cross-sectional area of the main groove 24.
There is an inconvenience that the drainage property is reduced due to the decrease in the cross-sectional area of the main groove 24, and the wet performance is reduced.

By changing the thickness of the belt layer, it is possible to provide the following functions and effects.

That is, as shown in FIG. 5, the thickness t of the rubber located between the cord or filament 19 of the inclined belt layer 20A and the cord 21 of the circumferential belt layer 20B.
1 in the tire width direction cross section in the tire width direction cross section.
To be larger than the central portion 42 in the tire width direction,
Specifically, the rubber thickness at the tire width direction end 40 is 2 times smaller than the rubber thickness at the tire width direction center 42.
The range L2 for maintaining the rubber thickness at the center portion 42 in the tire width direction is 50 to 90% of the width L1 of the inclined belt layer 20A with the tire equatorial plane CL as the center. The effect of so-called sandwich beams (TW Chou and FKK KO, ""
Textile Structural Compos
item "" Elsevir (1989)), and as a result, the bending rigidity in the tire circumferential direction is relatively lower at the tire width direction central portion 42 than at the tire width direction both end portions 40. As a result, the tire contact length is longer in the central region of the tread and shorter in both shoulder regions, so that the contact shape of the tire can be made closer to a round shape with reduced corners,
Thus, when traveling on a wet road surface, the water in front of the tire in the traveling direction can be quickly eliminated to the side of the tire, and the occurrence of hydroplaning can be suppressed.

Further, as shown in FIG. 5, the sum T of the thickness of the inclined belt layer 20A and the thickness of the circumferential belt layer 20B is:
FIG. 6 shows a case where the phenomenon that the unevenness corresponding to the cord appears near the center in the tire width direction on the inner circumferential surface of the tire after vulcanization due to the decrease at the center part in the tire width direction (cord appearance phenomenon). As shown, the thickness t2 of the rubber located between the cord 21 of the circumferential belt layer 20B and the inner circumferential surface of the tread rubber is larger at the tire width direction center portion 42 than at the tire width direction end portion 40. By doing so, the sum T of the thickness of the inclined belt layer 20A and the thickness of the circumferential belt layer 20B can be made uniform over the tire width direction,
The code appearance phenomenon can be suppressed. (Test Example) In order to confirm the action of the present invention (suppression of air column resonance (noise) level), the following test was performed.

Here, the test tire had the same shape as the pneumatic radial tire 10 of the embodiment, except for the cross-sectional area (cross-sectional shape) of the main groove 24. That is, by changing only the width while the depth of the main groove 24 is constant (8 mm), the cross-sectional areas of the main grooves of Comparative Examples 1 to 4 and Examples 1 to 3 are respectively 30 mm ² , 64 mm ² , 80 mm ² ,
120 mm ² , 125 mm ² , 150 mm ² , 170 mm ²
It is what it was.

In the test, a test vehicle having test tires mounted on four wheels was coasted at a speed of 50 km / h, and the noise was measured with a fixed microphone 7.5 mm laterally from the vehicle center line and 1.2 mm high. Things. The difference between the passing maximum noise level and the passing maximum noise level of Comparative Example 3 is expressed in dB (A) with reference to the reference (0 dB (A)). It should be noted that a region where the value was suppressed by 0.3 dB or more with respect to Comparative Example 3 was regarded as having a significant difference.

[0098]

[Table 1]

As shown in the test results, it was confirmed that the noise level can be surely suppressed by setting the cross-sectional area of the main groove 24 to 125 mm ² or more.

[0100]

As described above, the pneumatic radial tire of the present invention has the above-described structure, and therefore has an excellent effect of reducing the noise level while maintaining a light weight and high-speed durability.

[Brief description of the drawings]

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

FIG. 2 is a plan view of a belt layer of the pneumatic radial tire according to the first embodiment of the present invention.

FIG. 3 is a tread plan view of the pneumatic radial tire according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between a circumferential main groove cross-sectional area of a pneumatic radial tire and noise.

FIG. 5 is a cross-sectional view of a belt layer of a pneumatic radial tire according to another example.

FIG. 6 is a cross-sectional view of a belt layer of a pneumatic radial tire according to another example.

FIGS. 7A and 7B are diagrams illustrating a method for measuring the elastic modulus of a rubber covering a circumferential belt layer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Pneumatic radial tire 12 Bead core 14 Carcass 16 Tread part 19 Steel cord (cord) 20A Inclined belt layer 20B Circumferential belt layer 21 Organic fiber cord (cord) 24 Circumferential main groove

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B60C 9/00 B60C 9/20 D 9/20 G 9/22 B 11/00 F 9/22 D02G 3 / 48 11/00 B60C 11/04 H D02G 3/48

Claims (15)

[Claims] 1. A one-layer inclined belt in which a plurality of cords or filaments extending at an angle to a tire equatorial plane are arranged on the outer periphery of a crown portion of a toroidal carcass that straddles at least a pair of bead cores. Layer, at least one circumferential belt layer in which a plurality of cords are arranged substantially parallel to the tire equatorial plane and located on the inclined belt layer, and a tire radially outward of the circumferential belt layer. In a pneumatic radial tire having a tread provided with a circumferential groove, a cross-sectional area of the circumferential groove on the tire equatorial plane side is 125 mm ^2.
A pneumatic radial tire as described above. 2. The cord of the circumferential belt layer is made of polyethylene terephthalate fiber or nylon fiber, has a twin-twisted structure, and has a total denier number DT of 1000d to 60d.
When the number of twists of this cord is T (number of times / 10 cm) and the specific gravity is ρ, the twist coefficient Nt is Nt = T × (0.139 × DT / 2 × 1 / ρ) ^{1 / 2} x 1
The pneumatic radial tire according to claim 1, wherein the range is 0 ⁻³ ≦ 0.3. 3. The cord of the circumferential belt layer is made of polyethylene naphthalate fiber, has a twin twist structure, and has a total denier number DT in the range of 1000d to 6000d.
Assuming that the number of twists of this cord is T (number of times / 10 cm) and the specific gravity is ρ, the twist coefficient Nt is Nt = T × (0.139 × DT / 2 × 1 / ρ) ^1/2 × 1
The pneumatic radial tire according to claim 1, wherein the range is 0 ^-3 ≤0.6. 4. The cord of the circumferential belt layer is made of vinylon fiber, has a twin twist structure, and has a total denier number DT of 1
If the number of twists of this cord is T (number of times / 10 cm) and the specific gravity is ρ, the twist coefficient Nt is Nt = T × (0.139 × DT / 2 × 1 / ρ) ^1/2 x 1
The pneumatic radial tire according to claim 1, wherein the range is 0 ^-3 ≤0.6. 5. The cord of the circumferential belt layer is made of aramid fiber, has a twin twist structure, and has a total denier number DT of 1
If the number of twists of this cord is T (number of times / 10 cm) and the specific gravity is ρ, the twist coefficient Nt is Nt = T × (0.139 × DT / 2 × 1 / ρ) ^1/2 x 1
The pneumatic radial tire according to claim 1, wherein the range is 0 ⁻³ ≧ 0.3. 6. A tangent loss ta of a cord of the circumferential belt layer.
nδ is initial tension 1kgf / strain, strain amplitude 0.1%, frequency 2
6. The temperature is 0.3 or less under the condition of 0 Hz and an ambient temperature of 25.degree.
The pneumatic radial tire according to the item. 7. The pneumatic radial tire according to claim 1, wherein the cord in the circumferential belt layer is a twisted steel cord having an elastic modulus of 3000 kgf / mm ² or more. 8. The elastic modulus of the rubber covering the circumferential belt layer is:
The pneumatic radial tire according to any one of claims 1 to 7, wherein the pneumatic radial tire is 200 kgf / mm ² or more. 9. The pneumatic radial tire according to claim 1, wherein the cord of the circumferential belt layer is spirally wound. 10. The pneumatic radial tire according to claim 1, wherein the cord or filament of the inclined belt layer is made of a steel material. 11. The cord or filament of the inclined belt layer has an inclination angle of 15 ° to 45 ° with respect to the tire equatorial plane.
The angle is in the range of °.
0. The pneumatic radial tire according to any one of 0. 12. The thickness (tl) of the rubber located between the cord or filament of the inclined belt layer and the cord of the circumferential belt layer is set at the tire width direction end in the tire width direction cross section. The tire according to any one of claims 1 to 11, which is larger than a central portion in a tire width direction.
The pneumatic radial tire according to the item. 13. The thickness (t2) of rubber located between the cord of the circumferential belt layer and the inner peripheral surface of the tread rubber.
13. The pneumatic radial tire according to claim 12, wherein, in the cross section in the tire width direction, the center is made larger at the center in the tire width direction than at the end in the tire width direction. 14. The pneumatic radial tire according to claim 1, wherein the circumferential belt layer has at least two layers at a central portion in a tire width direction. 15. The tire according to claim 1, wherein the circumferential belt layer has at least two layers at an end in a tire width direction.
15. The pneumatic radial tire according to any one of items 14 to 14.