JP3322935B2 - Pneumatic radial tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire which uses a belt layer made of a steel cord to reduce its weight and has improved high-speed durability.

[0002]

2. Description of the Related Art In recent years, the problem of global environmental pollution and depletion of petroleum resources has led to a strong demand for low fuel consumption of vehicles. As one of the measures, weight reduction of pneumatic radial tires is a major technical problem. One of them attracts attention.
Steel cord is used for the belt layer of pneumatic radial tires because it has remarkably excellent tensile strength and tensile modulus compared to other organic fiber cords. Had become. However, existing organic fiber cords have a small tensile strength and tensile modulus and cannot exhibit tire performance equivalent to that of steel cords, and for the time being, it is necessary to rely on steel cords for the time being.

[0003] As measures for achieving weight reduction on the premise of using a steel cord, reduction in the amount of wire used and reduction in the amount of tread rubber (reduction in rubber gauge) can be considered.
As one of the means, it can be proposed that a steel cord in which a plurality of wires are formed into a stranded wire is constituted only by a single wire. If you use a single wire cord like this,
The cord diameter at the same wire cross-sectional area can be made smaller than that of the stranded wire, and thereby the distance from the groove bottom of the groove provided on the tread surface to the steel cord surface closest to the tread surface, that is, the tread of the tread Since the gauge under the groove (rubber gauge) and the gauge between the cords of the belt layer (rubber gauge) can be reduced, the amount of rubber can be reduced and the weight of the tire can be reduced. Moreover, in the case of a single wire, the rubber completely covers the periphery of the wire, so that it is possible to improve the corrosion fatigue resistance due to water absorption and the durability against the decrease in adhesion.

[0004] However, the cord of a single wire having such features is also rigid since it has no twist, and therefore has a drawback in that the durability against bending deformation and compression deformation due to repeated load is small. In addition, there is a problem that the insufficient wire durability causes wire breakage more frequently than the conventional tire using a stranded wire cord and causes a reduction in belt durability.

On the other hand, a method of reducing the amount of tread rubber of a pneumatic radial tire is not only an effective means for making the tire lighter, but also a method for reducing the centrifugal force during high-speed rotation (running). It has the effect of improving durability. However, when the amount of the tread rubber is reduced, it is necessary to reduce the thickness of the under-groove gauge of the tread.
Normally, the under-groove gauge is in the range of 3.0 to 4.5 mm, but if it is thinner than 3.0 mm, moisture on the road surface will diffuse and penetrate the rubber layer under the groove and it will easily reach the steel cord,
There is a problem that the water-resistant adhesiveness of the steel cord rubber is reduced, and separation of the belt layer is likely to occur. Moreover, a large strain is concentrated on the bottom of the groove during running, and the steel cord belt layer is repeatedly bent in a moisture-absorbing state, so that there is a problem that the cord is easily broken and the high-speed durability is reduced.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to reduce the rubber gauge by using a single wire cord, thereby reducing the weight as compared with the case of using a stranded wire cord and reducing the gauge under the groove. Accordingly, it is an object of the present invention to provide a pneumatic radial tire that achieves weight reduction by reducing the amount of tread rubber, and has improved water-resistant adhesiveness and, in turn, improved high-speed durability.

[0007]

According to the present invention, there is provided a pneumatic radial tire in which at least one belt layer including a steel cord is disposed on an outer peripheral side of a carcass layer of a tread and a groove is provided on a tread surface. A steel cord is shaped into a two-dimensional waveform along its longitudinal direction, and a brass plating layer is provided on the surface. The surface of the brass plating layer has a Ni plating of 2 to 12% by weight based on the total plating amount.
And a parameter F for specifying a two-dimensional waveform, a diameter d of the single-wire wire, a pitch length P of the waveform, and a two-dimensional waveform.
d) / P (where h indicates the height of the waveform) is 0.28 (mm) ≦ d ≦ 0.60 (mm) P ≧ 9.1d−1.55 (mm) 0.0025 ≦ F ≦ 0.06, and The above object can be achieved by a pneumatic radial tire in which a steel cord is arranged so that a two-dimensional surface of a corrugation is parallel to a tread surface.

Hereinafter, the present invention will be described in more detail. According to the present invention, a single-wire steel wire (element wire) used as a steel cord for a pneumatic radial tire is subjected to brass plating, and a three-element alloy layer containing a specific amount of Ni is formed on the surface of the brass plating layer. Let me know. This can improve the water-resistant adhesiveness of the single-wire steel cord, so even if the tire under the groove on the tread surface is set to 1.0 mm to 3.0 mm, which is smaller than the conventional 3.0 to 4.5 mm, the weight of the groove bottom can be reduced. The cord is less likely to be broken at a portion corresponding to the above, and the high-speed durability of the tire can be improved.

The single-wire steel wire used in the present invention is first plated with a brass having a zinc content of, for example, 60 to 70% by weight, that is, a mixture of copper and zinc by a diffusion plating method, and then overlaid thereon. It can be manufactured by plating Ni. The brass has an α phase and a β phase alloy phase, but the α phase is a face center cubic (FaceC
Entered Cubic (hereinafter abbreviated as FCC) Formability is superior to that of β phase because of its structure. Such an α phase is formed by sufficiently diffusing. On the other hand, Ni
Since it has a CC structure, when mixed with the above-mentioned brass plating of the α-phase, the entire structure becomes a uniform FCC structure and has good workability. For this reason, in order to form a three-element alloy layer on the surface of a steel wire, an α-phase brass is formed once, an oxide film is removed, and N
It is preferable that i is attached and Ni is diffused and mixed into the α-phase brass by the heat during wire drawing. Like the steel wire used for the steel cord of a conventional pneumatic tire (see, for example, JP-A-55-50486 and JP-A-55-105548), the above three elements of copper, zinc and Ni are used. When the mixture is plated, the brass produces an intermediate layer other than the α phase which is hardly deformed, so that the workability is poor.

[0010] The steel cord composed of a single-wire steel wire used in the present invention is 2500 mm from the surface of the steel wire on which a brass plating layer having a total Ni content of 12% is formed as shown in FIG.
As shown in the example of the quantitative distribution of Ni, copper, and zinc in the angstrom region, the amount of Ni increases in the region of 50 to 200 angstrom from the surface.

FIG. 5 shows that when the surface of a single-wire steel wire is subjected to brass plating and a Ni-rich three-element alloy layer is formed on the surface of the brass plating layer as described above, the Ni content in the three-element alloy layer is reduced. It shows the relationship between the content and the amount of rubber attached to the steel wire (by the following measurement method). The solid line A in FIG. 5 indicates that the sample was placed in 70 ° C. warm water.
The amount of rubber attached (water-resistant adhesion) measured after immersion for a week is shown, and the broken line B represents the amount of rubber attached (water-resistant adhesion) measured after immersion for 4 weeks. From this FIG.
When the i content is 2% by weight or more, the rubber coverage (water-resistant adhesiveness) is good, but when the content is 4% by weight or more, the rubber coverage (water-resistant adhesiveness) is 90% under any conditions. It can be seen that the above is shown. Further, even if the Ni content is more than 12% by weight, the rubber coverage (water-resistant adhesiveness) saturates without further improvement. Therefore, in the present invention, the Ni content in the three-element alloy layer on the surface of the single-wire steel wire is set to 2 to 12% by weight, preferably 4 to 12% by weight. If the amount is less than 2% by weight, the effect of improving the adhesiveness is low, and there is a possibility that a fatigue breaking phenomenon may occur. On the contrary, if it exceeds 12% by weight, the wire drawing property is reduced and the fatigue breaking phenomenon may occur.

The water resistance of the steel cord was evaluated by the following method. Evaluation method of water-resistant adhesiveness : After embedding a steel cord of a single-wire steel wire in unvulcanized rubber, vulcanizing it, immersing it in 70 ° C. warm water for 2 weeks and 4 weeks, then removing the steel wire from the embedded rubber The rubber was pulled out and the amount (%) of the rubber adhered to the surface was measured. The larger the amount of rubber, the better the water-resistant adhesion.

[0013] Such a steel wire can be obtained by known wire drawing. For example, after the steel material is hot-rolled and cooled as necessary, the obtained wire is plated with Cu, then Zn, and then energized, high-frequency, heated by a fluidized bed or the like to form a brass plating layer of a Cu-Zn alloy. After the formation, the oxide on the surface generated by heating is removed. Next, after applying Ni plating, wire drawing is performed, and the heat generated during wire drawing is diffused to the surface layer of the brass plating to form Ni, Cu and Z.
It can be manufactured by forming a three-element alloy layer made of n.

[0014] The steel wire having a Ni plating on the surface of the brass plating layer has a diameter of 0.28 to 0.60 mmφ.
And a single-wire steel cord plated with a three-element alloy layer. By setting the diameter of the steel wire within the above range, the bending fatigue as the steel cord belt layer can be made sufficient.

According to the present invention, the three-element alloy layer-coated single-wire steel wire used as a steel cord for a pneumatic radial tire is shaped into a two-dimensional waveform, thereby reducing the rigidity of the single-wire itself and repeatedly bending and deforming it. And excellent wire durability (belt durability) against compression deformation. However, even if the single wire is too large, the cornering power (steering stability) of the tire is reduced due to a decrease in the tensile modulus. By setting the parameter F specified from the diameter d of the single wire, the spiral diameter D thereof, and the pitch length P of the waveform in the range of 0.0025 to 0.06 as described above, both characteristics can be harmonized.

Hereinafter, the configuration of the present invention will be specifically described with reference to the drawings. In FIG. 1, 1 is a tread portion,
Reference numeral 2 denotes a carcass layer, which is wound around the pair of left and right bead cores 5 from the inside to the outside of the tire. The cord angle of the carcass layer 2 with respect to the tire circumferential directions E and E 'is substantially 90 degrees. On the outer peripheral side of the carcass layer 2 of the tread portion 1, two inner belt layers 4 having a cord angle of 5 to 40 ° with respect to the tire circumferential directions E and E ′, and reinforced with steel cords 40 intersecting each other, and an outer side Each of the belt layers 4 'is arranged over the entire circumference of the tire. On the surface of the tread portion 1, a main groove 6 extending in the tire circumferential direction E, E 'and a sub groove 7 intersecting the main groove 6 are provided.

In the present invention, as shown in FIG. 3, the steel cord 40 for reinforcing the belt layers 4, 4 'is composed of a two-dimensional corrugated single wire, and the single wire preferably has a tensile strength. When it is 320 kgf / mm ² or more and the diameter d is 0.28 mm to 0.60 mm, it is possible to exhibit a sufficient reinforcing effect equal to or more than that of the stranded wire cord. In order to enable the high tensile strength as described above, for example, if the carbon content of the steel wire is 0.8% by weight or more, the degree of wire drawing is increased, or the carbon content is 0.90 to 1.10% by weight.
And the chromium content is 0.1% by weight or more, preferably 0.1 to
It can be achieved by manufacturing from 0.4% by weight of high carbon steel. By setting the content of carbon and chromium in the above range, not only the tensile strength of the single wire but also the toughness and fatigue resistance are improved. You can also.

If the diameter d of the single wire is less than 0.28 mm, the bending stiffness of the belt layer is excessively reduced, so that it is difficult to suppress the wire breakage. On the other hand, if the diameter d exceeds 0.60 mm, the single wire becomes too rigid and the surface distortion accompanying compression deformation increases, so that the belt durability deteriorates.

As shown in FIG. 3, the single wire has a two-dimensional waveform having a height h larger than the diameter d and a pitch length P along its longitudinal direction. By shaping the single wire in this manner, the tensile modulus is reduced and the rigidity is reduced as compared with a straight single wire. Therefore, even with a single wire that is not twisted, the durability (fatigue resistance) against repeated bending loads and compressive loads is improved, and the durability when used for a belt layer is the same as that of using a stranded wire cord, or It can be further improved. However, if the degree of molding of this single wire is too large, the tensile modulus is significantly reduced, the lateral stiffness of the belt layer is reduced, and the cornering power is reduced. It will be difficult to secure.

The above-described characteristics of the single wire are based on the difference (h−h) between the height h of the shaped two-dimensional waveform and the wire diameter d.
d) and the pitch length P. That is, associating with the parameter F = (h−d) / P defined from the difference (h−d) and the pitch length P, as described below with reference to Table 1 and FIG. Correlation with fatigue property and tensile modulus can be made clearer, and furthermore, correlation with belt layer durability and cornering power (steering stability) becomes clear. In the present invention, this parameter F is set to 0.0025 to 0.06.

Table 1 shows the relationship between the two-dimensional waveform parameter F of the single wire and the fatigue resistance to repeated bending loads performed under the following measurement conditions. As is evident from the results in Table 1, when a single wire is spirally shaped with a parameter F = 0.0025, the fatigue resistance effect is more pronounced than that of a straight single wire (F = 0). You can do it. Furthermore, F = 0.
If it is set to 04 or more, almost no broken wire is recognized.

Fatigue resistance measurement method : As shown in FIG. 6, one single wire 40 is embedded in a rubber block 60 having a size of 12.5 mm × 12.5 mm × 20.0 mm, and both ends thereof are 12.5 mm × 12.5 mm. × 1
A 5.0 mm brass support block 70 is adhered so that both ends of the single wire 40 are connected to the support block 70 to prepare a measurement sample S. Prepare 10 of these samples S,
As shown in FIG. 7, it is attached between a pair of rotating plates T and T ', and the extension lines of both rotating shafts U and U' are set so as to form an angle θ. And max
1.5% compression strain is applied to the rubber block 60. After rotating both the rotating plates T and T 'set in this way 4 million times, the presence or absence of breakage of the single wire 40 in each sample S was examined, and the number of breaks was displayed as a percentage.

[0023]

[Table 1]

On the other hand, FIG. 8 shows a relationship between a two-dimensional waveform parameter F and a tensile modulus of a single wire having a diameter = 0.30 mm and a pitch P of a waveform of 0.4 mm.
FIG. 8 shows that the tensile modulus decreases as the parameter F increases. From the relationship with the cornering power based on the belt layer, it is necessary to set the tensile elastic modulus of the single wire to at least about 1.3 × 10 ⁴ kgf / mm ² , so that the upper limit of the parameter F is 0.06. .

In the present invention, when such a single wire is used as a reinforcing cord for the belt layer, the two-dimensional waveform is arranged so as to be parallel to the tread surface. With such an arrangement, the under-groove gauge t from the groove bottom of the main groove 6 formed in the tread to the single wire 40 of the outermost belt layer 4 'can be reduced (see FIG. 2), thereby reducing the amount of rubber. It is possible to reduce the weight and weight. Further, the weight can be reduced by reducing the distance a (gauge between plies) between the single wires 40 constituting the inner belt layer 4 and the outer belt layer 4 ', and the cornering power is increased to increase the interlayer shear force. It is possible. Moreover, since the wire is a single wire, the cord diameter can be reduced when the wire has the same cross-sectional area as compared with the stranded wire cord. Further, the periphery thereof can be completely covered with the coating rubber, so that it can have excellent water resistance and rust resistance.

Further, in the present invention, the pitch length of the waveform of the single wire must be in the range of P ≧ 9.1d−1.55 (mm). Spiral pitch length P is 9.1d-1.55 (mm)
If it is less than this, fatigue resistance decreases due to excessive bending, which is not preferable. The upper limit of the pitch length P is not particularly limited. In particular, by providing the three-element alloy layer on the surface of a single wire, a decrease in fatigue resistance can be suppressed even with a larger pitch length. In particular, pitch length
20 mm or less is preferable.

In the present invention, the under-groove gauge t can be set in the range of 1.0 to 3.0 mm by the above-described effect. By setting the under-groove gauge t to 1.0 mm or more, corrosion fatigue due to water absorption can be prevented, and belt wire breakage can be prevented. On the other hand, by setting the under-groove gauge t to 3.0 mm or less, the effect of reducing the weight can be secured. Also,
The gauge a between plies is 0.15 for radial tires for passenger cars.
It is better to be within the range of ~ 0.8mm. Set the gauge a between plies to 0.
By setting the thickness to 15 mm or more, it is possible to suppress the interlayer shear strain from becoming too large, and to suppress separation and belt wire breakage. On the other hand, when the thickness is 0.80 mm or less, sufficient interlayer shear strain can be imparted, and good cornering power and high-speed durability can be secured. 0.4 to 1.2 mm for heavy duty radial tires such as trucks and buses
It is better to The present invention is suitable mainly for application to pneumatic radial tires for passenger cars, but is also applicable to pneumatic tires for other uses such as for trucks and buses.

[0028]

EXAMPLES Hereinafter, the present invention will be further described with reference to Examples, but it goes without saying that the present invention is not limited to these Examples. As described below, the tire size, the carcass cord, the width of the inner and outer belt layers and the cord angle with respect to the tire circumferential direction, the pitch length P of the waveform of the single wire, the gauge a between the plies of the belt layer, and the gauge t below the groove are set to a common size. Otherwise, as shown in Table 2, the tensile strength of the single wire,
Diameter d, pitch length, parameter F, Ni in plating layer
Twenty kinds of radial tires, Comparative Examples 1 to 9 and Examples (Invention) Tires 1 to 11 having different contents, the number of ends and the under-groove gauge t were produced. The surface of the single-wire wire was previously subjected to brass plating of Cu / Zn by an ordinary method, and then nickel of the amount shown in Table 2 was plated thereon.

Tire size: 175 / 70R13 Carcass cord: Polyester fiber cord 1500D / 2 Belt layer cord structure: Single line Inner belt layer width = 120mm Outer belt layer width = 110mm Belt cord angle to tire circumferential direction = 20 ° Single line Pitch length of wire corrugation P = 4.0mm Gauge between plies a = 0.60mm

For further comparison, a steel cord was used in which two strands of wire having a diameter d = 0.28 mm were formed into a stranded wire having a cord structure of 1 × 2, and a belt layer was formed with 49/50 mm width end numbers. Manufactured a conventional tire having the same configuration as the comparative tire 1 (control example). With respect to these 21 types of radial tires, cornering power, high-speed durability by a drum test after moisture absorption, slalom durability (belt durability), and a weight reduction index were evaluated by the following methods. Table 2 shows the results.

Cornering power : Test tire pressure
At 200kPa (2.0kgf / cm ² ), rim is assembled to 13 × 5-J rim,
It runs on a drum with a diameter of 1707.6 mm at a speed of 10 km / hr under a load of 2942 N (300 kgf / cm ² ) and a slip angle of 1 ° to the right.
The average of the absolute values of the lateral force at the time of (1) and the lateral force at a slip angle of 1 ° to the left was measured. Indices are shown as indices using the measured value of the conventional tire as a reference (100). The larger this index value is, the larger the CP is, and the more excellent the steering stability is.

Lightening index : The ratio of weight reduction of each tire when the tire weight of a conventional tire is set as a reference (100) is expressed in%. Indices are shown as indices using the measured value of the conventional tire as a reference (100). The smaller the index value, the lighter the weight.

High-speed durability : The test tire is inflated to an air pressure of 220 kPa.
(2.2kgf / cm ² ) and assembled to a 13 × 5-J rim, 70 ° C ×
After being humidified by being left in an atmosphere of 98% RH for 45 days, it was run on a drum having a diameter of 1707.6 mm under a load of 4119 N (420 kgf / cm ² ) at a speed of 81 km / hr for 2 hours. After 12
When the speed was increased to 1 km / hr and thereafter the running speed was increased by 8 km / hr every 30 minutes to continue the running, the running speed at the time of the tire failure was evaluated. In addition,
The test was terminated when the speed reached 185 km / hr and no trouble occurred even after continuing for 30 minutes. It was indicated by an index using the measured value of the conventional tire as a reference (100).
The higher the index value, the better the high-speed durability.

Slalom durability : The test tire was subjected to an air pressure of 17
At 0 kPa (1.7 kgf / cm ² ), the rim was assembled to a 13 × 5-J rim, and the humidity was adjusted in the same manner as in high-speed durability. 350kgf) ± 2157
Under the condition of fluctuation of N (220kgf), load and slip angle are 0.067h
The vehicle was driven for 300 km while varying with the z-wave. After running, the test tire was incised, and the presence or absence of breakage of the belt cord was examined and evaluated.

[0035]

[Table 2]

[0036]

[Table 3]

As is evident from the results in Table 2, Examples 1 and 2 and Comparative Examples 1 and 2 in which the single wire diameter d was changed were used.
When d is less than 0.28 mm, the number of ends is high, the high-speed durability is insufficient, and the belt cord is broken (Comparative Example 1). Conversely, when d exceeds 0.60 mm, the high-speed durability is insufficient. And the belt cord is also broken (Comparative Example 2).
On the other hand, good results were obtained within the range of 0.28 to 0.60 mm (Examples 1 and 2).

In Examples 3 and 4 and Comparative Example 3 in which the pitch P of the single spiral was changed, P was 9.1d-1.55.
If it is less than 1.635 mm, the fatigue resistance is reduced and the belt cord is broken (Comparative Example 3), whereas good results are obtained in Examples 3 and 4, which are within the scope of the present invention. Was.

In Examples 5 to 6 and Comparative Examples 4 to 5 in which the parameter F of the single spiral was changed, the F value was 0.0025.
In Comparative Example 4 below, the fatigue resistance is insufficient and the belt cord is broken. On the other hand, when it exceeds 0.06, the elasticity decreases and the cornering power decreases (Comparative Example 5). On the other hand, in Examples 5 and 6, which are within the scope of the present invention, good results were obtained.

In Examples 7 to 9 and Comparative Examples 6 and 7 in which the Ni plating amount of the single spiral wire was changed, in Comparative Example 6 in which the Ni content was less than 2% by weight, the effect of improving the adhesion was not sufficient, so that the belt cord was Fatigue breaks due to moisture absorption, and conversely 12
If the content is more than 10% by weight, the drawability of the belt cord is reduced, so that the belt cord is broken by fatigue (Comparative Example 7). On the other hand, in Examples 7 to 9 within the scope of the present invention, good results were obtained.

Examples 10-11 are other examples according to the present invention, with good results.

[0042]

According to the present invention, the steel cord of the belt layer is constituted by a single-wire spiral wire whose surface is coated with a three-element alloy layer containing Ni, and the weight can be reduced. By shaping the shape into a three-dimensional waveform and setting the parameter F for specifying the waveform within a certain range, the rigidity inherent in the single wire is relaxed, good fatigue resistance is maintained, and the wire is not excessively flexible. Therefore, a decrease in steering stability can be suppressed. Further, by coating the surface with a three-element alloy layer containing Ni, it is possible to effectively solve the tire durability under more severe moisture absorption conditions, which is a problem particularly when the under-groove gauge is particularly reduced. it can. Moreover, in the present invention, by arranging the single wire so that its waveform is parallel to the tread surface, it is possible to reduce the gauge t under the groove of the tread and the gauge a between the plies of the belt layer, thereby reducing the amount of rubber. Therefore, it is possible to further reduce the weight, to impart an interlayer shear strain, and to further improve the steering stability.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view of a main part of a pneumatic radial tire for a passenger car according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing a main part of the tire of FIG. 1;

FIG. 3 is a side view showing an example of a two-dimensional corrugated single wire used in the present invention.

FIG. 4 is a graph showing the change (distribution) of the amounts of Ni, copper and zinc in a region from the surface of a steel wire on which a brass plating layer having a total Ni content of 12% is formed to 2500 Å.

FIG. 5 is a graph showing a relationship between a Ni content of a three-element alloy layer on a surface of a brass plating layer of a steel wire and a rubber coating amount.

FIG. 6 is a perspective view showing a shape of a sample for measuring fatigue resistance of a single wire.

FIG. 7 is a diagram schematically illustrating an apparatus for measuring fatigue resistance of a single wire.

FIG. 8 is a graph showing a relationship between a parameter F of a single wire and a tensile modulus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Tread part 2 ... Carcass layer 4 ... Inner belt layer 4 '... Outer (outermost) belt layer 6 ... Main groove 7 ... Sub-groove 40 ... Single wire d ... Single wire diameter h ... Wave height P ... Wave shape Pitch length

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-51-47702 (JP, A) JP-A-48-63961 (JP, A) JP-A-47-34576 (JP, A) JP-A-2- 92703 (JP, A) JP-A-4-281081 (JP, A) JP-A-62-288634 (JP, A) JP-A-1-259040 (JP, A) JP-A-1-201454 (JP, A) Japanese Utility Model Application No. 4-84395 (JP, U) Japanese Utility Model Application No. 5-46997 (JP, U) (58) Fields surveyed (Int. Cl. ⁷ , DB name) B60C 9/00 B60C 9/18-9/20 D07B 1/06

Claims (1)

(57) [Claims] 1. A pneumatic radial tire in which at least one belt layer including a steel cord is disposed on an outer peripheral side of a carcass layer of a tread and a groove is formed on a tread surface, the steel cord is arranged along a longitudinal direction thereof. A single-wire steel in which a two-dimensional waveform is molded, a brass plating layer is provided on the surface, and a three-element alloy layer containing 2 to 12% by weight of Ni with respect to the total plating amount is formed on the surface of the brass plating layer. A diameter d of the single wire, a pitch length P of the waveform, and a parameter F = (h−d) / P (where h indicates the height of the waveform) for specifying a two-dimensional waveform. 0.28 (mm) ≤ d ≤ 0.60 (mm) P ≥ 9.1 d-1.55 (mm) 0.0025 ≤ F ≤ 0.06, and the steel cord is arranged such that the two-dimensional surface of the waveform is parallel to the tread surface. Arranged pneumatic radio Rutaiya.