JP3027679B2 - Radial tire for high speed heavy load - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-speed heavy-load radial tire having improved durability of a bead portion.

[0002]

2. Description of the Related Art In recent years, tires used under high-load, high-speed conditions, for example, tires for aircraft, have structural durability.
Radial structures are being adopted to improve running performance and weight reduction.

However, since such an aircraft radial tire is used under a high load condition as described above, the bead portion is largely bent and deformed. A large stress acts on the part, and its internal temperature rises greatly. Due to such deformation and temperature rise, adhesion between the bead core and the rubber such as the topping of the carcass, the bead apex and the topping rubber of the bead filler is reduced, and peeling occurs between the bead core substrate and the rubber.

[0004]

In order to improve the bonding performance between the bead core and the rubber around the bead core, a method of forming the bead core by using a metal plated steel element wire has been proposed. Stable adhesion performance could not be obtained only by metal plating.

[0005] The inventors of the present invention have conducted various studies to solve the above-mentioned problems. As a result, in addition to applying metal plating to the steel strand, a rubber coating covering the bead core base formed using the steel strand having the above-described structure is provided. By providing the layer, it is possible to prevent peeling of the bead core and members such as carcass, bead apex, and bead filler disposed around the bead core. It has been found that the durability of the present invention can be improved, and the present invention has been completed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a high-speed heavy-load radial tire having improved durability of a bead portion.

[0007]

SUMMARY OF THE INVENTION The present invention provides a bead core substrate formed by winding a plurality of layers of a steel wire having a metal plating on the surface thereof, and a bead core substrate disposed on the outer peripheral surface thereof. A rubber covering layer, and the rubber thickness of the rubber covering layer is 0.3
This is a high-speed heavy-load radial tire provided with a bead core having a diameter of at least 1.8 mm and at most 1.8 mm.

The rubber coating layer has a complex elastic modulus E * of 80 to 80.
It is formed by a rubber composition of 200 kgf / cm ² .

The rubber coating layer is made of rubber polymer 100
0.5 to 5.0 parts by weight of a cobalt salt with respect to parts by weight, and the steel wire has a Cu content of 60 to 75% by weight and a Zn content of 25 to 40% by weight. / Zn plating is 0.3 ~ per kg of steel wire
More preferably, the metal plating is performed with an adhesion amount of 0.8 g.

[0010]

The bead core substrate is formed by winding a plurality of steel wires each having a surface plated with metal in a plurality of layers. This prevents rusting of the steel wire and increases the durability of the bead core, and also enhances the adhesion between the rubber coating layer and the bead base.

The bead core substrate is covered with a rubber coating layer. Therefore, the bead core substrate does not come into direct contact with the carcass and the bead apex, and the rubber coating layer provided for coating can select the rubber composition mainly based on the adhesion to the bead core substrate. The bead core formed by the above can securely adhere to the bead portion.

By providing such a rubber coating layer, a strong adhesive reaction layer is formed on the surface of the bead core, and the adhesion between the bead core substrate and the rubber can be improved.

The thickness of the rubber at the thinnest portion of the rubber coating layer is not less than 0.3 mm and not more than 1.8 mm. If the rubber thickness is less than 0.3 mm, good adhesion cannot be obtained, and if it exceeds 1.8 mm, the rubber thickness of the rubber coating layer becomes excessively large and the bead portion generates a large amount of heat when the tire rotates.

As described above, by applying metal plating to the steel wire and providing the rubber coating layer organically combined and integrated, it is possible to suppress a decrease in adhesive strength due to heat generation of the bead portion due to tire rotation. Thus, peeling of the bead core can be prevented, and the durability of the bead portion can be increased.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings, taking an example in which a high-speed heavy-load radial tire is an aircraft tire.

In FIG. 1, which shows a normal internal pressure state in which the tire is mounted on a normal rim R and filled with a normal internal pressure, a radial tire 1 for high-speed heavy load includes a tread portion 12 and sidewall portions extending inward in the tire radial direction from both ends thereof. 13, 13
And bead portions 2 and 2 located at the inner ends of the respective sidewall portions 13. Each bead portion 2 has a bead core 3
On the other hand, a carcass 16 is bridged between the bead cores 3, and a belt layer 17 is wound radially outward of the carcass 16. In the present embodiment, the carcass 16 and the belt layer 17 The cut breaker layer 18 is disposed between the two.

The carcass 16 extends from the tread portion 12 to both sides and extends from the tread portion 12 to the bead portion 2 through the sidewall portion 13 and to the bead portion 2. An inner layer 16A comprising a plurality of, for example, four, winding plies provided with a folded portion 16b wound outward from the inner layer, and a bead portion 2 disposed outside the inner layer and passing from the tread portion 12 to the sidewall portion 13 to the bead portion 2. In this embodiment, the outer layer 6B is formed of one or a plurality of, in this example, two lowering plies, extending in the tire axial direction outside the folded portion 16b of the hoisting ply.
And The winding ply and the lowering ply have a radial configuration in which carcass cords made of organic fibers such as nylon, rayon, polyester, and aromatic polyamide are arranged at an angle of 75 to 90 degrees with respect to the tire equator C, and in this example, 85 degrees. None, each ply is oriented differently as the carcass cords intersect between the plies.

A bead apex 14 made of a hard rubber extending in a tapered shape is provided outside the bead core 2 in the tire radial direction, and is provided between the main body 16a of the winding ply 16A, the folded portion 16b, and the lowering ply 16B. The working shear force is reduced.

The belt layer 17 comprises a plurality of belt plies in this example, which are sequentially stacked from the carcass 16 side to the tread surface side. Each belt ply has a ply width in the tire axial direction. It is set to be larger than the ply width of the belt ply adjacent on the outside. Each belt ply has a belt cord made of an organic or inorganic fiber such as nylon, rayon, polyester, aromatic polyamide, carbon or the like arranged substantially parallel to the tire equator C, and in this example, to the tire equator C. are doing.

The cut breaker layer 18 is formed by coating a breaker cord using an organic or inorganic fiber such as nylon, rayon, polyester, aromatic polyamide, or carbon with the tire equator C.
In this example, the breaker ply is formed by one or a plurality of sheets arranged at an inclination of 19 degrees or less, in this example, two sheets in this example. Each breaker ply is oriented differently so that the breaker codes cross each other between the plies.

As shown in FIG. 2, the bead core 3 comprises a bead core base 4 and a rubber coating layer 5 disposed on the outer peripheral surface thereof and covering the bead core base 4.

The bead base 4 is formed by winding a steel base line 6 into a plurality of layers as shown in FIG.

In this embodiment, a plurality of surrounding steel wires 6B are arranged in four layers around the steel wire 6A of the core disposed at the center, and the cross section is substantially circular. The bead core base 4 is formed.

In this embodiment, the core steel wire 6A has a wire diameter of 6 mm, and the surrounding steel wire 6B has a wire diameter of 2.2 mm.

The surrounding steel wire 6B is made of a hard wire,
For example, piano wire S specified in JIS G 3502
In addition to WRS77A or 82A, JIS G 3506
Can be adopted. The diameter of the steel strand is preferably in the range of 0.8 to 3.0 mm.
The core steel wire 6A may be a hard or soft steel wire, and preferably has a diameter larger than the surrounding wire 6B.

The steel wire 6 is subjected to a metal plating process prior to the formation of the bead core base 4. In this example, the metal plating has a Cu content of 60 to 75% by weight,
This is binary plating of Cu / Zn having a Zn content of 25 to 40%, and is performed with an adhesion amount of 0.3 to 0.8 g per kg of a steel wire.

The steel wire 6 has such a plating composition,
By applying metal plating according to the amount of plating, the adhesive strength between the metal coating and the rubber coating layer 5 can be increased.

If the amount of plating is less than 0.3 g per kg of steel wire, activation of the bonding reaction by plating is reduced, the bonding speed is reduced, and the vulcanization speed of the rubber coating layer 5 matching this is reduced. Angukure of the rubber during vulcanization is likely to occur when trying to obtain. Also 0.
If the amount exceeds 8 g, the activation of the bonding reaction by plating increases, and the bonding speed is increased. If an attempt is made to obtain a rubber vulcanization rate matching this, there is a risk of rubber burning.

The Cu / Zn plating is not particularly limited, and may be performed by a commonly used method such as a substitution method or a diffusion method. In addition, there is no particular limitation on a method of depositing a plating. Any plating may be used as long as it has the same degree of uniformity as the plating applied to the wire rod.

Generally, the compressive shearing force and heat generated by the deformation of the bead portion caused by the rotation of the tire reduce the adhesive force between the bead core base 4 and the rubber around the bead core substrate, causing peeling. Due to this peeling, looseness of the entire bead portion occurs between the carcass ply of the bead core, the bead apex of the bead core, and the surrounding members surrounding the bead core such as the bead filler, and the durability of the bead portion 2 is reduced. .

By providing the rubber coating layer 5 on the outside of the bead core base 4 formed by the steel strands 6 as in this embodiment, the adhesive strength between the bead base 4 and members disposed around the bead base 4 is improved. In addition, the propagation of the compressive shear force generated by the rotation of the tire to the bead core substrate is alleviated, and the decrease in the adhesive force can be suppressed.

The rubber coating layer 5 has a rubber thickness t at its thinnest portion of 0.3 mm or more and 1.8 mm or less. If the rubber thickness t is less than 0.3 mm, good results between the rubber forming the rubber coating layer 5 and the bead core substrate 4 cannot be obtained. This is because when the rubber thickness t is less than 0.3 mm, there is a shortage of sulfur that increases the adhesive strength. In addition, the impact force due to the rotation of the tire is propagated to the bead core base 4, and the adhesive strength between the bead base 4 and members disposed around the bead base 4 is reduced. On the other hand, when the rubber thickness t exceeds 1.8 mm, the heat generated by the bead core caused by the rotation of the tire becomes large, the deterioration of the rubber coating layer 5 is accelerated, and the durability decreases in any case. In order to enhance the durability, it is more preferable that the rubber thickness t is in the range of 0.5 to 1.5 mm.

The rubber coating layer 5 is formed of a rubber composition having a complex elastic modulus E * of the rubber of 80 to 200 kgf / cm ² . When the complex elastic modulus E * is less than 80 kgf / cm ² , the rigidity is insufficient, the movement of the bead core base 4 is remarkably increased by the rotation of the tire, and the heat generation is increased, while 200 kgf / cm ^2.
When the thickness exceeds the above range, the impact caused by the rotation of the tire propagates to the bead core substrate, so that the bead substrate 4 and the rubber coating layer 5 are liable to be separated.

The rubber coating layer 5 is made of a rubber polymer 10
2 to 10 parts by weight of sulfur is blended with 0 parts by weight to obtain good adhesion between rubber crosslinking and the metal plating, and 0.5 to 5.0 parts by weight to obtain more stable adhesion. It contains a cobalt salt. As a typical example of rubber polymer,
Natural rubber, a blend of natural rubber and isoprene rubber,
There are blends of natural rubber, isoprene rubber and liquid isoprene rubber.

If the amount of the cobalt salt is less than 0.5 part by weight, the effect of stabilizing the adhesive strength is not obtained. If the amount is more than 5.0 parts by weight, a change in screw at the time of raw rubber is large, and the production process is hindered.

FIGS. 3, 4, and 5 show other examples of the bead core 3. FIG. In FIG. 3, a long steel wire 6 is spirally wound into a plurality of layers by metal plating to form a bead core base 4 having a rectangular cross section, and the bead core base 4 is covered with a rubber coating layer 5. .

FIG. 4 shows another example in which a steel wire 6 is wound to form a bead core substrate having a hexagonal cross section. In FIG. 5, a core obtained by winding the steel wire 6 in a hexagonal shape is shown. A bead core base 4 is formed by winding an outer layer 4D in the form of a steel wire 6 around the outside of the portion 4C. As described above, the bead core base 4 can be formed in various cross-sectional shapes.

[0038]

[Specific Example] A tire having a tire size of 46 × 17R20 and having the configuration shown in FIGS. 1 and 2 was prototyped according to the specifications shown in Table 1 (Examples 1 to 5), and its performance was tested. . In addition, the tire of the conventional structure without the rubber coating layer (conventional example 1) and the tire (comparative example) other than the structure of the present invention were also tested and their performances were compared.

Table 2 shows the rubber composition in which the content ratio of the cobalt salt was changed (Reference Examples 1 to 5) and the rubber composition.
(Examples 6 to 9) in which the complex elastic modulus was changed by changing as shown in FIG.

The metal plating applied to the steel strand is as follows:
In Examples, Conventional Examples, Comparative Examples, and Reference Examples, Cu was 6
The adhesion amount was adjusted to 0.3 to 0.8 g per kg of the steel wire by Cu / Zn plating containing 0 to 75% by weight.

The test method is as follows. 1) Complex elastic modulus E * Viscoelastic spectrometer VES-F- manufactured by Iwamoto Seisakusho
Using type III, temperature 70 ° C, initial strain 10%, dynamic strain ± 1
% And a frequency of 10 Hz.

2) Adhesion between Rubber Coating Layer and Bead Core Substrate Five-step evaluation is performed, and the larger the better, the better.

3) Heat generation of bead portion A test was performed by a 100% taxi simulation using a drum tester based on the United States Aviation Administration Standard TSO-C62C, and at the end of 100 cycles, the temperature of the bead portion was measured. It was indicated by an index with 3 as 100. The smaller the value, the lower the exothermic temperature.

4) Change in Screw of Rubber Coating Layer After leaving each sample for 20 days, a Mooney viscosity test according to JIS K-6300 is performed. If the index is 100 or less, it indicates that the screw has decreased. Table 1 shows test results
Shown in

[0045]

[Table 1]

[0046]

[Table 2]

As a result of the test, good results are obtained when the rubber thickness t of the rubber coating layer is 0.3 mm or more, preferably 0.5 mm or more. It was confirmed that.

Further, as shown in Reference Examples 1 to 5, the Mooney bis change is small in the range of 0.5 to 5.0% by weight of the cobalt salt, and the bis change is small in the case of containing 7.0% by weight. It was confirmed that it was large.

[0049] Further, the intended complex elastic modulus E of the rubber-coated layer as in Reference Example 6-9 * is 80~200kgf / cm ² was good without swelling of the bead portion, too soft at 60 kgf / cm ² In addition, it was found that at 300 kgf / cm ² , the bead portion was inferior in durability due to being too hard.

[0050]

As described above, the radial tire for high-speed heavy load of the present invention having the above-described structure suppresses heat generation of the bead core generated when the tire rotates, prevents peeling of the bead core, and improves durability of the bead portion. Enhance the nature.

[Brief description of the drawings]

FIG. 1 is a right half sectional view of a tire showing one embodiment of the present invention.

FIG. 2 is a sectional view showing the bead core.

FIG. 3 is a cross-sectional view showing another example of a bead core.

FIG. 4 is a cross-sectional view showing another example of a bead core.

FIG. 5 is a sectional view showing another example of a bead core.

[Description of Signs] 2 Bead portion 3 Bead core 4 Bead core base 5 Rubber coating layer 6 Steel strand t Rubber thickness

Continuation of front page (56) References JP-A-3-54007 (JP, A) JP-A-52-109204 (JP, A) JP-A-61-285104 (JP, A) JP-A-2-256503 (JP, A) , A) Japanese Utility Model Showa 63-107207 (JP, U) JP-B 47-15122 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60C 15/04

Claims (2)

(57) [Claims] 1. A bead core substrate formed by winding a plurality of layers of a steel wire having a metal plating on a surface thereof, and a rubber coating layer disposed on an outer peripheral surface of the bead core substrate and covering the bead core substrate. A bead core having a thickness of 0.3 mm or more and 1.8 mm or less is provided in a bead portion at a portion where the rubber thickness of the rubber coating layer is the thinnest, and the rubber coating layer has a complex elastic modulus E * of 80 to 200 kgf.
/ Cm ² rubber composition for high-speed heavy load. 2. The rubber coating layer contains 0.5 to 5.0 parts by weight of a cobalt salt with respect to 100 parts by weight of a rubber polymer, and the steel wire has a Cu content of 60% by weight.
Cu with a Zn content of 25 to 40% by weight
/ Zn plating 0.3-0.8g per kg of steel wire
Claim, characterized in that of the metal plated at a coverage 1
The radial tire for high-speed heavy load described .