JP2000203212A - Radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance both a road noise reducing effect and a tire property. SOLUTION: This radial tire is provided with a belt reinforcing layer 6 arranged to cover the whole widths of belt layers 4, 4' located in an outer circumferential side of a crown part of a carcass 2 formed ranging over between a pair of beads. The reiforcing layer 6 comprises at least one layer of a rubber layer reinforced with cords extended in a tire circumferential direction, at least the cords of a width-directional central part of the belt reinforcing layer 6 comprise polyethylene-2,6-naphthalate cords, and the cords of belt width- directional both-end parts comprise an organic fiber cord having 9.8 GPa or more of tensile elastic modulus.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radial tire, and more particularly to an improved technique of a belt reinforcing layer disposed over a belt layer.

[0002]

2. Description of the Related Art In recent years, as vehicles have been upgraded and upgraded in quality,
In particular, with respect to passenger cars, while the vibrations of vehicles and the improvement of ride comfort are rapidly progressing, low noise and high ride comfort are also required for characteristics required as tires. That is,
Along with the improvement of riding comfort, it is particularly desired to reduce noise generated in the vehicle. One of such noises is that a running tire picks up irregularities on a road surface, and the vibration is transmitted to vibrate air in the vehicle. Therefore, the demand for improvement of so-called road noise, which is generated based on the above, has become extremely high.

[0003] Conventionally, the road noise reduction methods that have been basically used are (1) a method of softening rubber in a tire tread portion, and (2) a reinforcement of a belt layer by changing a shape of a tire carcass. Technique to make
(3) A method of strengthening the belt circumferential rigidity by sandwiching all or both ends of the cross belt layer with a reinforcing layer obtained by rubberizing cords (for example, nylon cords) arranged in the circumferential direction. In order to eliminate the above joint, a method of winding the reinforcing layer around the belt layer outside in a helical manner (for example, see JP-A-6-24208) can be mentioned.

Since these methods have advantages and disadvantages as very general methods, each method is selected or used in combination according to the purpose. In particular, the method (3) is a method satisfying the improvement of high-speed durability rather than the reduction of road noise.
In particular, it is becoming mainstream.

As a special method, (4) as disclosed in Japanese Patent Application Laid-Open No. 5-238205, a cord arranged in the circumferential direction is sandwiched between a carcass layer and a belt layer by a high modulus rubber sheet. A method of disposing a composite layer and (5) a method of performing partial reinforcement according to a tire vibration mode as disclosed in Japanese Patent Application Laid-Open No. 3-253406 are also known. Further, as the application of the tire in which the rubberized nylon cord is spirally wound around the outermost layer of the belt in the method (3), in particular, for the purpose of improving the high-speed durability and the high-speed level, for example, (6) A method of winding an elastic modulus cord (for example, see Japanese Unexamined Patent Publication No.
No. 7, JP-A-1-145203) and (7) In order to improve the vulcanization of the tire, a cord wound spirally around the outermost layer is formed by twisting filaments having a high elastic modulus and a low elastic modulus. (See, for example, Japanese Unexamined Patent Publication No.
No. 47204), and (8)
An example in which the fiber material to be twisted is limited in order to improve the noise performance of the method (7) (Japanese Patent Laid-Open No. 6-305304), and (9) an organic textile is provided on both sides of the belt layer in the tire axial direction. Many methods are known, such as an example using a reinforcing layer made of a cord (Japanese Patent Application Laid-Open No. 6-115312). , The effect of reducing road noise is recognized, albeit slightly.

Further, recently, (10) JP-A-9-6
As described in Japanese Patent No. 6705, the cord of the belt reinforcing layer is strictly limited in consideration of the physical properties at the time of vulcanizing and using the tire, or the cord of the belt reinforcing layer is made of polyethylene.
By a method using 2,6-naphthalate fiber cord,
Rolling resistance, along with a higher level of road noise reduction
Attempts have also been made to improve steering stability and high-speed durability. Also, (11) a method of using a high elasticity cord at both ends and a low elasticity cord at the center of the belt reinforcing layer, or a method of increasing the cord insertion at both ends and decreasing the cord insertion at the center is known. (See, for example,
93504, JP-A-4-31107, JP-A-9-2
No. 77803), all of these inventions aim to enhance ride comfort, road noise, high-speed durability and steering stability by making the tread both ends relatively high rigidity with respect to the tread center portion. It was done.

[0007]

However, the method of reducing road noise according to the above-mentioned method (1) is characterized in that in the method (1), even if the road noise can be reduced by softening the tread rubber, the wear resistance is reduced. Is not practical because the steering stability greatly deteriorates. Further, in the method (2), even if the tension of the belt layer of the tire can be enhanced, the lateral rigidity and The cornering performance is deteriorated, and the parts other than the tread are grounded, and the appearance is not good. Further, in the method (3), although there are some effects on the improvement of high-speed durability and the reduction of road noise, they are still not satisfactory. In the methods (4) and (5) as application examples of the method (3),
Although the effect is higher than that of the method (3), the degree of improvement is small and the durability with respect to high speed is insufficient.
In the method of (1), it is difficult to make practically, and the steering stability is deteriorated. The method using the composite cord as in the methods (7) and (8) also has an inflection in the stress-elongation curve. Therefore, the behavior of the code differs between a so-called large input and a small input, and the effect of reducing road noise over a wide range of 100 to 500 Hz is insufficient. Also,
These combined codes are not practically preferable because the speed dependency of the road noise reduction effect is large.
Further, in the method (9), although there is a slight effect of reducing road noise, cord characteristics required for the belt reinforcing layer are not specified, and the cord characteristics are not fully utilized in tire performance. The road noise reduction effect is also inadequate, and only as described in that example, even if a high modulus cord such as a normal aromatic polyamide is simply wound into a spiral, the road noise cannot be sufficiently reduced. At the same time, the steering stability is greatly deteriorated.
In the method (10), among the methods (1) to (8), the road noise, the driving stability, and the high-speed durability are most efficiently improved, but the quality of future vehicles will be improved. However, it is not enough to cope with high-grade.

Further, the method (11) is an example in which the rigidity of both ends of the belt reinforcing layer is made higher than that of the central portion, thereby achieving the effect of tightening the tread portion in a well-balanced manner. Because only the elongation, modulus, driving density, etc. are controlled, the characteristics of the material of the organic fiber cord itself are utilized only in the form of cord elongation and modulus, making it optimal for input during tire running. Although the code material was not selected, although some effects were recognized, road noise reduction could not be achieved at a high level.

In general, a method of winding a nylon cord in a helical manner as a belt reinforcing layer is effective for reducing road noise during tire running in order to increase belt tension in the circumferential direction. It is known that the higher the elasticity, the better the road noise reduction. For example, road noise is reduced by winding a polyester cord, which is generally higher in elasticity than a 6,6-nylon cord, than by winding a 6,6-nylon cord all over.

However, during tire production (particularly during vulcanization)
There is a step of pressing a green tire against a vulcanizing mold. In this step, the tire is generally greatly expanded (usually about 2 to 6%) at a tread center portion, so that it is simply wound in a spiral shape in the circumferential direction. In the method, when a cord having extremely high elasticity (for example, aramid cord) is used as a cord of the belt reinforcing layer, the cord of the belt reinforcing layer cannot be expanded completely, so that tire deformation occurs at the time of tire vulcanization molding. This remarkably occurs particularly in a tire tread center portion having a large expansion rate. On the contrary, this causes deterioration of road noise. Therefore, in order to reduce road noise, it is necessary to increase the elasticity of the cord of the belt reinforcing layer in consideration of the tire deformation.

As a method of compensating for these problems, the above-mentioned (7) using a high elastic specific cord as the reinforcing layer cord,
The techniques (8) and (10) are effective for reducing road noise. However, these techniques using a specific single material code have a limited effect on reducing road noise. Although there is an advantage that the manufacturing equipment can be simplified because it is a single material, the effect of improving road noise is one step away.

The effect of reducing road noise is particularly
It is effective to make the tightening in the circumferential direction at the tire shoulder relatively higher than at the center. In this regard, the method of (11), in which the cord elastic modulus, the number of shots, and the like are changed between the shoulder portion and the center portion to give the necessary physical properties to each, is conceptually effective, but
Since the selection of the cord material and the like were not aimed at reducing the road noise, the level was insufficient for reducing the road noise.

It is an object of the present invention to provide a radial tire that achieves a high level of road noise reduction by devising a belt reinforcing layer made of a specific organic fiber cord under such circumstances.

[0014]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventor has paid particular attention to the selection of combinations of the materials of the fiber cords used for the belt reinforcing layer, and as a result of intensive studies, the radial tire has been obtained by the following means. It has been found that both the road noise reduction and the tire properties are improved, and the present invention has been completed.

The radial tire of the present invention includes a belt reinforcing layer disposed over the entire width of a belt layer (preferably at least two layers) located on the outer peripheral side of a crown portion of a carcass formed between a pair of beads. In a radial tire, the belt reinforcing layer is made of at least one rubber layer reinforced with a cord extending in the tire circumferential direction, and at least a cord in the center in the width direction of the belt reinforcing layer is made of polyethylene-2,6-naphthalate cord. Wherein the cords at both ends in the belt width direction are made of organic fiber cords having a tensile modulus of elasticity of 9.8 GPa or more.

In a preferred first embodiment, the belt reinforcing layer has a center portion in the width direction of the belt reinforcing layer of polyethylene-2,6.
-At least one rubber layer reinforced with a naphthalate cord and reinforced at both ends in the belt width direction with an organic fiber cord having a tensile modulus of 9.8 GPa or more.

In a second preferred embodiment, the belt reinforcing layer has polyethylene-2,6 at the center in the width direction of the belt reinforcing layer.
A rubber layer reinforced with a naphthalate cord and reinforced at both ends in the belt width direction with an organic fiber cord having a tensile elastic modulus of 9.8 GPa or more, at least one layer, and only at both ends in the belt width direction; And at least one pair of rubber layers reinforced with an organic fiber cord of 0.8 GPa or more.

In a third preferred embodiment, the belt reinforcing layer comprises at least one rubber layer reinforced with polyethylene-2,6-naphthalate cord at both ends as well as at the center in the width direction of the belt reinforcing layer; And at least one pair of rubber layers reinforced with an organic fiber cord having a tensile modulus of 9.8 GPa or more at both ends in the width direction.

Further, the belt reinforcing layer of the present invention comprises a narrow strip formed by rubberizing a polyethylene-2,6-naphthalate cord or an organic fiber cord having a tensile elastic modulus of 9.8 GPa or more in the tire circumferential direction. It is formed by spirally winding it endlessly, whereby the cord is substantially parallel to the tire circumferential direction.

[0020]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail. At least the central part of the belt reinforcing layer of the present invention is polyethylene-
When a super-high elastic cord made of aramid, polyvinyl alcohol, steel, or the like is used, the tire product may be deformed. When an elastic cord is used, although the tagging effect as a belt reinforcing layer is sufficient, it is insufficient for suppressing vibration of a tread tread for reducing road noise, but polyethylene-2,6 is used.
The naphthalate code does not have these disadvantages.

Further, both ends of the belt reinforcing layer of the present invention are reinforced with an organic fiber cord having a tensile elastic modulus of 9.8 GPa or more. However, this is relatively high elasticity in order to effectively reduce road noise. It is necessary.

Further, the both ends of the belt reinforcing layer are constituted by high elastic cords wound substantially at 0 ° in the tire circumferential direction. This increases the belt tension in the tire circumferential direction and increases the tread portion. This is because the road noise can be reduced by the so-called barrier effect that does not transmit the vibration due to the unevenness of the road surface received at the tire to the tire side part,
In particular, since a large tension is applied to the both end portions of the tread in the circumferential direction on the tread surface of the tire, increasing the elastic modulus of the reinforcing material in this portion is particularly effective.

On the other hand, in the central portion of the belt reinforcing layer, the tensile strength tends to be weaker on the tread surface in contact with the ground than in the non-contact state. A softer, relatively lower modulus cord is better. However, the low elastic modulus here is limited only when compared with the cords at both ends, and the higher the absolute elastic modulus, the better. That is, when a high elasticity fiber cord is used in the center, it is preferable to arrange cords having higher elastic modulus at both ends.

Further, under the repeated input of tension and relaxation caused by the rolling of the tire, the loss characteristic of the belt reinforcing layer has a large effect on the road noise, and depends on the input of the elastic modulus, tan δ, etc. of the belt reinforcing layer. By appropriately selecting the cord material by matching the characteristics (the tendency of change) to the tire use conditions, the above-described road noise reduction can be further enhanced.

The present invention has been completed in view of the above findings. As described above, a polyethylene-2,6-naphthalate cord and a tensile modulus of 9.8 GPa are used as the cord of the belt reinforcing layer. By combining the above-mentioned organic fiber cords and providing a belt reinforcing layer arranged properly, the present inventors succeeded in effectively satisfying the reduction of road noise of a radial tire.

Next, an example of the radial tire according to the present invention will be described with reference to FIG. A pair of beads 1,1 '
A carcass 2 is disposed between the crown portions 3
, Two belt layers 4 and 4 ′ reinforced by steel cords are arranged, and a belt reinforcing layer 6 (exemplifying the structure of FIG. 2A) is formed outside the belt layers 4 and 4 ′ and inside the tread 5. ing.

FIG. 2 illustrates in a cross-sectional view the pattern of a belt reinforcing layer 6 arranged over the belt layers 4, 4 '. In FIG. 2A, the belt reinforcing layer 6 is a single layer, the central portion of the belt reinforcing layer in the width direction is reinforced with polyethylene-2,6-naphthalate cord 7, and both ends in the belt width direction have a tensile elasticity of 9.8 GPa. It is reinforced with the organic fiber cord 8 described above.

In FIG. 2B, the belt reinforcing layer 6 has two layers, and the center of the two layers 6a and 6b in the belt reinforcing layer width direction is reinforced with polyethylene-2,6-naphthalate cord 7, and the belt width is increased. Both ends in the direction are reinforced with an organic fiber cord 8 having a tensile modulus of 9.8 GPa or more. In FIG. 2C, the belt reinforcing layer 6 is such that the inner layer 6a covers the entire width of the belt layer, and the central part in the width direction of the belt reinforcing layer is polyethylene-2,6.
-Reinforced with a naphthalate cord 7, both ends in the belt width direction are reinforced with an organic fiber cord 8 having a tensile elastic modulus of 9.8 GPa or more, and an outer layer 6b is provided only at both ends in the belt width direction, It is reinforced with an organic fiber cord 8 having a tensile modulus of 9.8 GPa or more.

In FIG. 2 (d), the belt reinforcing layer 6 has an inner layer 6a covering the entire width of the belt layer, and not only the central part in the width direction of the belt reinforcing layer but also both ends are made of polyethylene-2,6-naphthalate cord 7. The outer layer 6b is reinforced with only one pair at both ends in the belt width direction, and has a tensile modulus of 9.8 GP.
a. FIG.
In (e), the belt reinforcing layer 6 is such that the inner layer 6a covers the entire width of the belt layer, and not only the center part in the width direction of the belt reinforcing layer but also both ends are reinforced with polyethylene-2,6-naphthalate cord 7, The outer layer 6b is reinforced with an organic fiber cord 8 having a tensile elastic modulus of 9.8 GPa or more in two pairs only at both ends in the belt width direction.

The method for producing the polyethylene-2,6-naphthalate cord according to the present invention may be a conventional method for producing a fiber using a cord for a tire, and is not particularly limited (Japanese Unexamined Patent Publication (Kokai) No. Heisei 5). 163612).

Polyethylene-2,6-naphthalate is
If 85 mol% or more of polyethylene-2,6-naphthalate can be used without any problem, it can be synthesized by any of ordinary melt polymerization and solid phase polymerization. The resin chips substantially polyethylene-2,6-naphthalate (intrinsic viscosity 0.72) obtained by such a method are melt-spun. The spinning speed is set to 600 m / min, and a heating cylinder having an atmospheric temperature of 340 ° C. and a length of 44 cm is set immediately below the spinneret. An oil agent is applied to the spun undrawn yarn with an oiling roller, and the undrawn yarn is wound. Next, the obtained undrawn yarn is subjected to 1% pretension, and then subjected to a shrink heat setting at a relaxation rate of 2.2% between a heated roll and a non-heated roll at 227 ° C., and wound at 300 m / min. . The temperature of the spinning machine was 300 to 3 in the latter half of the extruder where the polymer was melted.
It is preferable to set the temperature from 15 ° C. to 318 ° C. thereafter. Also, after passing through the heating cylinder,
It is preferable to cool and solidify at a relative humidity of 65% and a temperature of 25 ° C. over a length of 35 cm. In this way, a raw yarn of polyethylene-2,6-naphthalate is obtained.

The polyethylene obtained as described above
The yarn of 2,6-naphthalate cord has a twist coefficient of 115.
By adjusting so as to be 0 to 2600, a cord used for the belt reinforcing layer is obtained. [The twist coefficient R = N ×
√D, N is the number of twists of the cord (times / 10 cm), D
Is the total display fineness (decitex) of the code. Further, in the dip treatment step in the manufacture of the radial tire according to the present invention, after applying the adhesive, the cord may be subjected to a tension heat treatment of the cord by a drying section, a first heat stretching section (heat set zone), and a second heat stretching. In a part (normalizing zone), heat treatment is performed under predetermined conditions. Specifically, it is immersed in a resorcinol-formalin latex adhesive (see below), the treatment temperature in the drying zone is 170 ° C., the treatment time is 60 to 160 seconds, and the treatment temperature in the heat setting zone and the normalizing zone is 250-270 ° C., the treatment time is 60-160 seconds, and the heat set zone cord tension is 3.5.
The cord tension is set in the range of 3 to 9.71 mN / dtex and the normalizing zone cord tension is in the range of 0.26 to 4.41 mN / dtex. Further, a two-stage treatment using a reactive adhesive, such as an epoxy adhesive, may be performed.

[RFL adhesive]: The adhesive is resorcinol.
Mixing polysulfide and resorcinol-rich resorcinol-formaldehyde condensate in a solids ratio of 20: 100,
Then, 18 parts by weight of solid content was taken out, and 9 parts by weight of 28% ammonia water was added thereto, and water was further added to make the whole amount 50 parts by weight to completely dissolve, and then 50 parts by weight of resorcinol -What added formaldehyde condensate / latex (RFL) was used. Here, RFL was prepared to the following composition and aged for 48 hours or more. (Parts by weight) water 518.8 resorcinol 11.0 formalin (37%) 16.2 ammonium hydroxide (28%) 10.0 copolymer latex of vinylpyridine-styrene-butadiene (41%) 244.0

The properties of the thus obtained polyethylene-2,6-naphthalate cord used in the belt reinforcing layer of the present invention after heat treatment are as specified in JIS L1010.
The elongation at a constant load (W) defined by 17-1983 (7.7), for example, in the case of a double twist of 1670 dtex, the elongation at a 66N (Newton) load is:
It is preferably 1.8 to 2.7%. If the elongation percentage under a constant load is less than 1.8%, the thermal shrinkage of the polyethylene-2,6-naphthalate cord becomes too large, the tire uniformity becomes poor, and if it exceeds 2.7%, the belt is reinforced. This is because, as a layer, the effect of tightening in the tire circumferential direction is weakened, and high-speed durability is reduced.

The organic fiber cord having a tensile modulus of not less than 9.8 GPa disposed at both ends of the belt reinforcing layer (ie, both ends of the tread) may be a fiber used for a normal tire cord. There is no restriction. For example, aromatic polyamide fiber cord, polyolefin ketone fiber cord (polyethylene ketone fiber cord and the like) and the like can be mentioned.

Although the belt reinforcing layer has been described as being divided into a central portion and both end portions in the width direction of the belt reinforcing layer, these ratios are not particularly limited. In other words, it is preferable that one end width is 6 to 28% of the maximum width of the entire belt reinforcing layer. This is because if it is less than 6%, the road noise reduction effect decreases, and if it exceeds 28%, the tire properties at the center tend to deteriorate.

[0037]

EXAMPLES The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

In each of the examples and comparative examples, a tire having a tire size of 195 / 65R14 was manufactured. In addition,
The vulcanization condition of the tire was 180 ° C. × 13 minutes, and the post-cure inflation condition was an internal pressure of 0.25 MPa, 26
Minutes. The carcass cord used was a polyethylene terephthalate cord.

The test tire structure was a tubeless structure, and the belt had two layers (a first belt width of 150 mm and a second width of 140 mm) reinforced with steel cords. The steel cord has a 1 × 5 × 0.23 structure and the number of shots is 34.0.
Book / 5 cm, the angle of the first belt layer is 22 degrees left with respect to the circumferential direction, and the angle of the second belt layer is 2 degrees right with respect to the circumferential direction.
It was twice.

Further, in the belt reinforcing layer, the reinforcing cords are arranged at 0 to 5 ° C. in the tire circumferential direction, and the structure and cord type are as shown in Tables 2 and 3. The belt reinforcing layer was formed in the cord direction by rubberizing 5 to 20 predetermined organic fiber cords, forming a strip having a width of 5 to 20 mm, and spirally winding the strip in the tire circumferential direction. .

The reinforcing cords of the belt reinforcing layer, polyethylene-2,6-naphthalate cord, aramid fiber cord and polyethylene ketone fiber cord, are 1670 dt.
ex / 2, the number of chords is 5 for each chord
It is 0 / 5cm.

The following measurements and evaluations were performed for each of the above tires. Measurement method of tensile elasticity Carefully take out the belt reinforcement layer cord from the tire when it is not running new, without damaging it, carefully scrape off excess rubber attached to the cord with scissors,
A tensile load-elongation curve is drawn at room temperature (25 ± 2 ° C.) with an autograph (manufactured by Shimadzu Corporation) according to JIS LIO17. By converting the load axis of this load-elongation curve into a value obtained by dividing the load axis by the total number of decitex before tension, the curve was rewritten as a stress-elongation curve, and a tangent was drawn to the 7.94 mN / dtex load point of this curve. Find the slope of The value obtained by multiplying this value by [0.981 × specific gravity of fiber] is the tensile modulus (GPa) referred to herein.

Test tire for road noise test (internal pressure: 0.20 MPa, rim size: 6 J)
-14) mounted on four wheels of a 1800 cc, sedan-type car with a displacement of 2,800 passengers, traveling on a test course on a road noise evaluation road at a speed of 60 km / h, and the center side of the backrest portion of the driver's seat. With a sound collecting microphone attached to
A total sound pressure (decibel) of 0 to 500 Hz was measured. This value was expressed as an index, with the value of the control tire of Comparative Example 1 taken as 100. The higher this value, the better the road noise reduction effect.

Tire Property Evaluation Method Each tire was cut substantially parallel to the tire radial direction,
After buffing the cross-sectional surface, the belt gauge of the cross-section and the interlayer gauge of the belt reinforcing layer are visually observed. At this time, the one having a uniform gauge in the tire width direction is good (◎), the one which is not uniform but the interlayer gauge is sufficiently maintained is normal (○), the one which is not uniform and the interlayer gauge is partially Insufficient ones were judged to be slightly defective (も の), and those having poor properties enough to cause problems in durability and safety were judged as defective (×).
◎ to △ are levels at which there is no problem in terms of durability and safety. Needless to say, the ◎ indicates that the tire has higher safety.

[0045]

[Table 1]

[0046]

[Table 2]

In Examples 1 to 3, the belt reinforcing layer had the structure shown in FIG.
It is reinforced with naphthalate cord (PEN), and both ends are reinforced with aramid fiber cord (aramid) or polyethylene ketone fiber cord (PEK). Example 4-
Reference numeral 6 denotes a structure in which the belt reinforcing layer is as shown in FIG. 2 (d), the inner layer is reinforced over the entire width with polyethylene-2,6-naphthalate cord, and the outer layer is a pair of aramid fiber cord or polyethylene ketone fiber cord. It is reinforced with. In Examples 7 and 8, the belt reinforcing layer has a structure shown in FIG. 2C, the center of the inner layer is reinforced with polyethylene-2,6-naphthalate cord, and both ends are aramid fiber cord or polyethylene ketone fiber. The outer layer is reinforced with a pair of aramid fiber cords or polyethylene ketone fiber cords.

Comparative Examples 1 to 4 are conventional types, and have a structure shown in FIG. 3F and are reinforced with only one layer and a cord of the same fiber material over the entire width. Comparative Example 1 is a polyethylene-2,6-naphthalate cord (PEN), and Comparative Examples 2 to 4 are aramid fiber cords. Comparative Examples 5 and 6 are also conventional types, and have the structure shown in FIG. 3G, in which both the inner layer and the outer layer are reinforced with cords of the same fiber material. Comparative Example 5 is a polyethylene-2,6-naphthalate cord, and Comparative Example 6 is an aramid fiber cord. Comparative Examples 7, 8, and 9 have the structures shown in (a), (d), and (c) of FIG. 2, respectively, and the cords that reinforce both ends have a tensile modulus of less than 9.8 GPa. is there.

In each of the embodiments, both the road noise reduction effect and the tire properties are significantly improved.
On the other hand, in each of the comparative examples, only one of them was improved, but none of both was improved.

[0050]

As described above, according to the present invention,
A radial tire with significantly improved road noise reduction and tire properties can be realized.

[Brief description of the drawings]

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

FIG. 2 is a sectional view showing a belt reinforcing layer according to the present invention.

FIG. 3 is a sectional view showing a belt reinforcing layer of a conventional radial tire.

[Description of Signs] 1.1 'Bead 2 Carcass 4 Belt Layer 5 Tread 6 Belt Reinforcement Layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B60C 9/22 B60C 9/22 BC

Claims (10)

[Claims] 1. A radial tire provided with a belt reinforcing layer disposed over the entire width of a belt layer located on an outer peripheral side of a crown portion of a carcass formed between a pair of beads, wherein the belt reinforcing layer is formed on the tire periphery. At least one rubber layer reinforced by a cord extending in the width direction, at least a cord at the center in the width direction of the belt reinforcing layer is made of polyethylene-2,6-naphthalate cord, and cords at both ends in the belt width direction are tensile elastic moduli. A radial tire comprising an organic fiber cord of 9.8 GPa or more. 2. The belt reinforcing layer has a central portion in the width direction of the belt reinforcing layer reinforced with polyethylene-2,6-naphthalate cord, and both ends in the belt width direction have a tensile modulus of 9.8 GPa.
The radial tire according to claim 1, comprising at least one rubber layer reinforced with the organic fiber cord. 3. The radial tire according to claim 2, wherein the rubber layer is a single layer. 4. The radial tire according to claim 2, wherein the two rubber layers are provided. 5. The belt reinforcing layer has a central portion in the width direction of the belt reinforcing layer reinforced with polyethylene-2,6-naphthalate cord, and both ends in the belt width direction have a tensile modulus of 9.8 GPa.
A rubber layer reinforced with the above organic fiber cord, at least one layer, and at least one pair of rubber layers reinforced only with the organic fiber cord having a tensile modulus of 9.8 GPa or more only at both ends in the belt width direction. The radial tire according to claim 1, wherein: 6. The belt reinforcing layer has a central portion in the width direction of the belt reinforcing layer reinforced with polyethylene-2,6-naphthalate cord, and both ends in the belt width direction have a tensile modulus of 9.8 GPa.
A rubber layer reinforced with the above organic fiber cord, one layer and both ends in the belt width direction, and a tensile elastic modulus of 9.8 GPa
The radial tire according to claim 5, comprising a pair of rubber layers reinforced with the organic fiber cord. 7. A belt reinforcement layer comprising at least one rubber layer reinforced with a polyethylene-2,6-naphthalate cord at both ends as well as a central part in a width direction of the belt reinforcement layer;
Only at both ends in the belt width direction, tensile modulus 9.8 GP
2. The radial tire according to claim 1, comprising: at least one pair of rubber layers reinforced with at least a. 8. The belt reinforcing layer includes not only a central portion in the width direction of the belt reinforcing layer but also one rubber layer having both ends reinforced with a polyethylene-2,6-naphthalate cord, and only one end portion in the belt width direction. The radial tire according to claim 7, comprising a pair of rubber layers reinforced with an organic fiber cord having a tensile modulus of 9.8 GPa or more. 9. The belt reinforcing layer includes not only a central part in the width direction of the belt reinforcing layer but also a rubber layer whose both ends are reinforced with polyethylene-2,6-naphthalate cord, and only one layer and both ends in the belt width direction. The radial tire according to claim 7, comprising two pairs of rubber layers reinforced with an organic fiber cord having a tensile modulus of 9.8 GPa or more. 10. The radial tire according to claim 1, wherein at least two belt layers are provided.