JP3146327B2 - Pneumatic radial tires for passenger cars - 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 for a passenger car, which is improved in high-speed durability while reducing its weight.

[0002]

2. Description of the Related Art Due to recent problems of environmental pollution and depletion of petroleum resources, there has been a strong demand for fuel-efficient vehicles.
As part of this, weight reduction of pneumatic tires has been attracting attention as a major technical issue. The method of reducing the tread rubber amount of a radial tire for a passenger car is not only an effective means for reducing the weight of the tire, but also improves the high-speed durability by reducing the centrifugal force during high-speed rotation (running). It works. However, a measure to reduce the amount of tread rubber is to reduce the distance from the groove bottom of the groove provided on the tread surface to the steel cord surface closest to the tread surface (hereinafter, referred to as a groove-under gauge). I will be forced. 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, the water on the road surface diffuses and penetrates the under-groove rubber layer to easily reach the steel cord. The water-resistant adhesion to the coated rubber is reduced, and the separation of the belt layer is easily generated. 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.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic radial tire for a passenger car, which can reduce the weight of the tread rubber to reduce the weight and improve the high-speed durability.

[0004]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a pneumatic radial tire in which at least one belt layer made of a steel cord is disposed inside a tread and a groove is provided on a tread surface. A brass plating layer on the surface, and the brass plating layer has a surface of 2 to 12% by weight (2 to 30 atom%) of N based on the total plating amount.
The diameter of 0.12--forming a three-element alloy layer containing i
The belt layer is composed of a steel cord obtained by twisting 1 to 5 steel wires of 0.35 mmφ, and the distance from the groove bottom of the groove to the surface of the steel cord closest to the tread surface is 1.0 to 3 mm. 0.0mm range.

[0005] As described above, the steel wire (steel wire) constituting the belt layer 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. Thereby, in order to improve the water-resistant adhesiveness of the steel cord, even if the tire is made lighter by setting the under-groove gauge of the groove on the tread surface to 1.0 to 3.0 mm smaller than the conventional 3.0 to 4.5 mm, The cord is less likely to break at the portion corresponding to the groove bottom, and high-speed durability can be improved.

[0006] The steel wire of the present invention is prepared by first plating a brass having a zinc content of 60 to 70% by weight, that is, a mixture of copper and zinc, by diffusion plating, and then adding Ni thereon. It can be manufactured by plating. The brass has an α phase and a β phase alloy phase, and the α phase is a face center cubic (FaceC).
Since it forms an entered cubic (hereinafter abbreviated as FCC) structure, its workability is superior to that of the β phase. Such an α phase is formed by sufficiently diffusing.
On the other hand, since Ni also has an FCC structure, when mixed with the α-phase brass plating, the whole becomes a uniform FCC structure and has good workability. Therefore, in order to form a three-element alloy layer on the surface of the steel wire, an α-phase brass is formed once, the oxide film is removed and Ni is attached, and Ni is applied to the α-phase brass by the heat of diffusion. Is preferably mixed by diffusion. However, as in the case of a steel wire used for a steel cord in a conventional pneumatic tire (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.

The steel cord used in the present invention is shown in FIG.
As shown in the example of the quantitative distribution of Ni, copper, and zinc in the region of 2500 Å from the surface of the steel wire on which the brass plating layer having the total Ni content of 12% was formed, Ni in the region of 50 to 200 Å from the surface is shown. It can be seen that the amount of is increasing. Hereinafter, the configuration of the present invention will be specifically described with reference to the drawings.

1 and 2, reference numeral 1 denotes a tread portion;
Is 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. Between the tread portion 1 and the carcass layer, two inner belt layers 4 and outer (outermost) belt layers 4 'made of steel cord are respectively arranged over the entire circumference of the tire. The cord angles of the belt layers 4, 4 'with respect to the tire circumferential direction E, E' are 5 to 40 [deg.] And cross each other. Tread part 1
A main groove 6 extending in the tire circumferential direction E, E ′,
An intersecting sub-groove 7 is provided.

In the tire of the present invention having the above-described structure, as shown in FIG. 2, the thickness of the rubber under the groove from the groove bottom of the main groove 6 to the steel cord 40 of the outermost belt layer 4 ', that is, the gauge under the groove t is set in the range of 1.0 to 3.0 mm. Although the groove depth d of the main groove 6 is not particularly limited, it is 8.0 like the conventionally used one.
It is set to １11.0 mm.

Further, the steel wire (element wire) constituting the steel cord 40 of the belt layers 4 and 4 'is subjected to brass plating, and the surface of the brass plating layer further has a weight of 2 to 12 wt. %, Preferably 4-12
A three-element alloy layer containing Ni by weight is formed. That is, 50 to 20 from the surface of the plating layer
It is composed of a Ni-rich three-element alloy layer containing 2 to 30 atomic% of Ni in the range of 0 Å.

FIG. 4 shows a case where the surface of a steel wire is subjected to brass plating as described above, and a Ni-rich three-element alloy layer is formed on the surface of the brass plating layer. It shows a relationship between the amount and the amount of rubber attached to the steel wire (by the following measuring method). The solid line A in FIG. 4 represents the rubber coverage (water-resistant adhesion) measured after immersing the sample in 70 ° C. hot water for 2 weeks, and the broken line B represents the rubber measured after immersion for 4 weeks. Indicates the weight (water resistant adhesiveness). It can be seen from FIG. 4 that when the Ni content is 2% by weight or more, the rubber coverage (water-resistant adhesiveness) is good, but when the Ni content is 4% by weight or more, the rubber coverage (water-resistant adhesion) is obtained under any conditions. It can be seen that the characteristic ()) is 90% or more.

Further, even if the Ni content is more than 12% by weight, the rubber coverage (water-resistant adhesiveness) saturates without further improvement. The water resistance of the steel cord was evaluated by the following method. Evaluation method of water-resistant adhesiveness : A steel cord having a cord structure of 1 × 2 (0.30 mm) obtained by twisting steel wires is buried in unvulcanized rubber, vulcanized, and then placed in 70 ° C. hot water for 2 weeks. After immersion for 4 weeks, the steel cord was pulled out from the embedded rubber, and the amount (%) of the rubber attached 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, Ni
It can be manufactured by forming a three-element alloy layer composed of Ni, Cu, and Zn by plating and then drawing and diffusing it to the surface layer of the brass plating using heat generated during drawing. .

The steel wire having a three-element alloy layer formed on the surface of the brass plating layer has a diameter of 0.12 to 0.12.
Wire drawing is performed so as to be in a range of 0.35 mmφ, and a steel cord is formed by twisting 1 to 5 wires. The diameter of the steel wire shall be in the above range, and the number of twisted wires shall be 5
By making the steel cord belt layer or less, the bending fatigue property as a steel cord belt layer can be made sufficient.

Further, the cord structure of the steel cord can be 1 × 2, 1 × 3, 1 × 4, 1 × 5, etc. in addition to a single cord. The twist pitch and the like are not particularly limited. In the pneumatic radial tire of the present invention, the belt layer made of the steel cord is provided as a reinforcing layer of the tread, and the under-groove gauge of the groove formed on the tread surface is thinner than the conventional gauge of 3.0 to 4.5 mm. 1.
The range is from 0 to 3.0 mm. This under-groove gauge is 3.0
When the thickness is not more than mm, the amount of tread rubber can be reduced and the weight of the tire can be reduced. In addition, the weight reduction makes it possible to suppress the separation of the belt layer due to the centrifugal force at the time of high-speed running, thereby improving the high-speed durability.
On the other hand, by setting the thickness to 1.0 mm or more, a rubber thickness sufficient to protect the outermost belt layer is secured, and durability is imparted.

In the pneumatic radial tire according to the present invention, a steel cord obtained by twisting the above-mentioned steel wire is buried in coat rubber at a predetermined number of ends to form a belt constituting material, and then the belt constituting material is used as a carcass ply, tread, or the like. It can be manufactured by laminating together with other tire constituent materials on a forming drum to form a green tire, and vulcanizing and molding this green tire from a mold according to a conventional method.

[0017]

The tire size was 175 / 70R13, the carcass cord was a polyester fiber cord 1500D / 2, the diameter of the steel wire was 0.30mm, the number of steel cords inserted was 45 / 5cm, and the cord structure was 1 × 2.
(0.30) are common to each other, and as shown in Table 1,
Tires of the present invention of Examples 1 to 8 and comparative tires of Comparative Examples 1 to 9 were manufactured in which the Cu / Zn ratio of the brass plating, the Ni content of the surface layer thereof, and the under-groove gauge t were respectively different.

About these 17 types of radial tires,
High-speed durability and moisture resistance after moisture absorption are determined by the following drum test method.
Evaluate the durability of lalome, and use the following method to reduce the weight
Was evaluated. The results are shown in Table 1.High-speed durability after moisture absorption : Air pressure 2.1 kg / cm^TwoTester
Assemble the ears on a 13 × 5-J rim, 70 ° C × 98
% RH for 30 days in an atmosphere of% RH
After that, on a drum having a diameter of 1707.6 mm, 420 kg
And running at a speed of 121 km / hr,
The running speed is increased by 8 km / hr every 30 minutes.
Mileage until tire failure occurs
It was evaluated with the separation.Slalom durability after moisture absorption : Air pressure 1.7kg / cm^Twoof
Assemble the test tire on a 13 x 5-J rim and after absorbing moisture
After humidification in the same manner as high-speed durability, the diameter was 1707.6.
± 5 ° on 350 mm drum, 350 kg ± 22
After running under a load condition of 0 kgf, the load and slip
Flip angle is changed by a rectangular wave of 0.067hz to 300km
I ran. Cut the test tires after running and belt cord
The evaluation was made by examining the presence or absence of breakage. Lightening index : When the tire weight of Comparative Example 1 was set to 100
The weight reduction ratio of each tire was expressed in%.

[0019]

According to Table 1, the steel cord belt layer has a Ni content of 0% (no Ni plating) in the three-element alloy layer.
Comparing the tires of Comparative Examples 1 and 2 having different under-groove gauges and the tires of Comparative Example 3 having a Ni content of 1.0% and the under-groove gauge of 2.0 mm, respectively, It can be seen that as the lower gauge t becomes thinner, the weight-saving effect is improved (the drum high-speed durability after moisture absorption is the same), but the cord is broken and the slalom durability after moisture absorption is deteriorated.

On the other hand, the steel cord belt layer
The tire of Example 1 composed of a steel wire having a Ni content of 2% by weight in the element alloy layer and having a gauge below the groove of 3.0 mm shows the same weight reduction index as the tire of Comparative Example 2,
Both high-speed durability and slalom durability have been improved. Also, the Ni content was the same as in Example 1 and the under-groove gauge was set to 1.0.
Although the effect of improving the high-speed durability is small, the effect of improving the weight reduction index is remarkable for the tire of Example 2 having a thickness of mm.

The tire of Example 3 using a steel wire having a Ni content of 7% in the three-element alloy layer and the gauge under the groove being 2.0 mm has a high-speed durability, a slalom durability, and a weight reduction index. However, all have been further improved. In Example 3, the tire of Example 4 in which the under-groove gauge was set to 1.0 mm had a small effect of improving the high-speed durability, but had a large effect of improving the weight reduction index. However, even when the Ni content of the three-element alloy layer was 7%, the tire of Comparative Example 4 in which the gauge under the groove was 0.5 mm had a broken cord, deteriorated slalom durability, and had high-speed durability. Has also declined.

The Ni content in Example 5 was set to one of the upper limits of the present invention.
The tire with 2% and the under-groove gauge of 3 mm improves all of high-speed durability, slalom durability, and weight reduction index. In Example 5, the tire of Example 6 with the under-groove gauge of 1 mm was used. Although the high-speed durability is smaller than that of Example 5, the weight reduction index is significantly improved. But N
In the tires of Comparative Examples 5 and 6 in which the i content was 13% and 14%, the cord was broken regardless of the gauge under the groove, and the slalom durability was deteriorated.

In Comparative Example 1, the tire of Comparative Example 7 in which the under-groove gauge was extremely small and 0.5 mm was used, the weight reduction effect was great, but the high-speed durability of the drum after moisture absorption and the durability of the slalom after moisture absorption were remarkably reduced. . Comparative Example 8 in which the under-groove gauge was set to 2.5 mm and the Ni content was changed,
9 and the tires of Examples 7 and 8 in which the Ni content is within the specified range of the present invention, the tires of Examples 7 and 8 have improved high-speed durability, slalom durability, and lightening index. In each of the tire of Comparative Example 8 having a Ni content of 0% and the tire of Comparative Example 9 having a Ni content of 14%, the cord was broken and the slalom durability was reduced.

[0025]

According to the present invention, a steel cord constituting a belt layer is subjected to brass plating comprising Cu and Zn, and a three-element alloy layer containing a specific amount of Ni is formed on the surface of the brass plating layer. By forming the steel wire formed with the above, the water-resistant adhesiveness of the steel cord was improved.
Even if the tire is reduced in thickness within the range of 3.0 mm to reduce the weight of the tire, the occurrence of cord breakage can be reduced and the high-speed durability can be improved.

[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 tire of the present invention.

FIG. 2 is an enlarged sectional view of a main groove portion formed in a tread portion of FIG.

FIG. 3 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 having a 12% brass plating layer formed thereon to 2500 angstroms.

FIG. 4 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.

[Explanation of symbols]

Reference Signs List 1 tread portion 4 inner belt layer 4 'outer (outermost) belt layer 6 main groove 7 sub groove 40 steel cord t groove lower gauge d groove depth of main groove

Continuation of the front page (56) References JP-A-5-163365 (JP, A) JP-A-1-113232 (JP, A) JP-A-1-201454 (JP, A) JP-A-56-79005 (JP) , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B60C 9/00 D07B 1/06 B60C 11/04 B60C 11/13

Claims (1)

(57) [Claims] 1. A pneumatic radial tire in which at least one belt layer made of a steel cord is disposed inside a tread and a groove is formed on a tread surface, the pneumatic radial tire has a brass plating layer on the surface, and the surface of the brass plating layer Containing 2 to 12% by weight of Ni with respect to the total plating amount
The belt layer is composed of a steel cord formed by twisting 1 to 5 steel wires having a diameter of 0.12 to 0.35 mmφ on which an element alloy layer is formed, and the steel is positioned closest to the tread surface from the groove bottom of the groove. A pneumatic radial tire for a passenger car having a distance to a cord surface in a range of 1.0 to 3.0 mm.