JPH0542802A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To improve the separation property of a belt intervening between a carcass ply and tread rubber in a pneumatic radial tire. CONSTITUTION:In a belt having a structure comprising at least more than two layers of steel cords arranged crosswise between a tire carcass ply and tread rubber and at an angle of 10 to 30 degrees to the equatorial direction of the tire, the physical property of rubber covering the steel cords is such that Tan delta<E'X3.9e<-10>+0.07 and that 1.0X10<8>dyn/cm<2E'<4.0X10<8>dyn/cm<2>. In the belt structure, the physical property of the rubber covering the steel cords is thus optimized and thereby the durability of the belt is remarkably enhanced and the rate at which separation occurs at the end portion of the belt is reduced and the belt is very useful practically.

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, and more particularly to an improved belt separation property interposed between a carcass ply and a tread rubber.

[0002]

2. Description of the Related Art A radial tire has a plurality of code angles which are arranged substantially at right angles to the circumferential direction, and a carcass ply whose both ends are locked by a pair of bead cores and a tread rubber. The belt reinforcement layer of is wrapped around,
By increasing the rigidity of the tire tread portion, this belt layer has the effect of improving the fuel economy due to the steering stability, wear resistance and rolling resistance of the radial tire. However, the higher the rigidity of this belt, the more
The interlaminar shear strain at the belt end becomes excessive, so-called separation occurs here, and the durability life of the tire tends to deteriorate.

That is, in a pneumatic radial tire,
A high belt rigidity is required to support the stress due to the tire internal pressure, and on the other hand, it is required to reduce the shear strain between the layers rather than the belt rigidity especially at the both side edges of the belt. Different characteristics are required for the and marginal areas. As a factor to improve the belt separation resistance in both side edge areas of this belt,
It is known that the rubber coating the steel cord has high hardness and high elongation at break, and it is effective to improve the aging resistance and crack growth resistance. For example, JP-A-50-60
No. 904 proposes a method of optimizing a filler for rubber to achieve both breaking properties and fatigue resistance. In Japanese Patent Laid-Open No. 52-140103, a belt central portion and a belt end portion are proposed. A method has been proposed in which high hardness and high elongation at break are compatible with each other by adopting a concept of separating the roles of and.

[0004]

However, there is a limit to the compatibility of the rupture property and the crack resistance depending on the blending of rubber, and changing the rubber type at the belt end portion lowers the productivity. Lead to The present invention seeks to find a more effective solution by scrutinizing the mechanism of occurrence of belt separation, finds the optimum physical property conditions of rubber, and provides a concrete compounding means. That is the purpose.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the problems by specifying the physical properties of a steel cord-coated rubber which constitutes a belt of a pneumatic radial tire, and the gist of the invention is as follows. On the street. That is, in a pneumatic radial tire having a belt structure composed of at least two layers of steel cords, which is disposed between the tire carcass ply and the tread rubber and crossed at an angle of 10 to 30 degrees with respect to the tire equator direction. The physical properties of the rubber covering the steel cord constituting the belt are Tan δ <E ′ × 3.9e ⁻¹⁰ +0.07,
And 1.0 × 10 ⁸ dyn / cm ² <E ′ <4.0 × 1
The present invention provides a pneumatic radial tire having a characteristic of 0 ⁸ dyn / cm ² . And, particularly preferably, E'is 1.5 × 10 ^{8 to} 3.5 ×.
It is desirable to be in the range of 10 ⁸ dyn / cm ² .

[0006]

The present inventors have found that the belt separation and the
As a result of scrutinizing the relationship between the properties of the rubber coated with rubber, the tire creeps during running as a more effective factor than the conventional compatibility of fracture resistance, crack resistance, fatigue resistance, etc. It was found that it is important that the strain at the belt edge increases. Further, if the strain is simply reduced, the elastic modulus may be increased, but under a substantially constant strain input condition such as bad road endurance, the opposite effect is obtained. Here, the dynamic storage elastic modulus E ′ and It was found that there is an optimum region that holds between the tangent loss Tan δ.

That is, the strain (index) at the belt end, which causes the belt separation, is 199.1 × Tan δ-7.
It is represented by 66e ^-8 × E '+ 75.4, and it was found that the belt endurance can be greatly improved by setting the belt end strain to 90 (index) or less, and the present invention has been achieved.

At this time, the range of E'is 1.0 × 10
More than ⁸ dyn / cm ² , 4.0 × 10 ⁸ dyn / cm
² or less, preferably 1.5 × 10 ⁸ dyn / cm ² or more and 3.5 × 10 ⁸ dyn / cm ² or less, below which the initial strain becomes too large, and above this, bad roads This is because a constant distortion input such as durability has the opposite effect.

The dynamic storage elastic modulus E'and the loss tangent Ta
nδ is 25 using a spectrometer manufactured by Iwamoto Seisakusho
C., 52 Hz, initial load 160 gf, and 2% dynamic strain amplitude were measured as conditions.

The belt end strain during tire running is measured by measuring the circumferential length at normal internal pressure before and after actual running, and assuming that the growth amount is proportional to the increase amount during belt end shear strain during running. Displayed as an index.

The steel cord coated rubber having such characteristics can be obtained by the following compounding method. That is, the first is N, N'- which is a vulcanizing agent.
m-phenylene dimaleimide is a method of blending 0.5 to 4 parts by weight with respect to 100 parts by weight of rubber, the second is a nitrogen absorption specific surface area (N ₂ SA) of 65 to 100 m ² / g, and an oil absorption amount. (DBP) is 100-130ml / 100g
50 to 70 parts by weight of carbon black having the following physical properties is used. Thirdly, the compounding ratio of natural rubber to butadiene rubber is at least 40/60 to 80/20. The rubber physical properties described above can be achieved by using one or more of them. The nitrogen absorption specific surface area of the above carbon black is ASTM-D-3037-8.
Nitrogen adsorption specific surface area by 8B method, oil absorption is AST
It is the amount of dibutyl phthalate adsorbed according to the MD-2414-84 method.

[0012]

【Example】

(Rubber Property Test) First, a rubber having the physical properties of the present invention was manufactured by the above-mentioned compounding method. The composition and physical properties are shown in Table 1.

[0013]

[Table 1]

(Belt Separation Test) Next, with the above-mentioned various rubber compounds, a steel cord is coated to form a belt, which is placed between the carcass ply and the tread rubber to form a tire. did.

The belt durability, separation occurrence rate and comprehensive evaluation of such tires are also shown in Table 1. In the table, the belt durability is an index of the length of cracks that occur at the end of the belt when running on a good road (mainly highways) for about 100,000 km at 100% load, and the smaller this value is, the longer the durability. It has excellent properties. The separation occurrence rate is 150 to 180.
The rate of occurrence of belt separation is indexed after running about 40,000 km on a rough road (mainly gravel road) with a% load, and the smaller this value, the better the durability. The comprehensive evaluation is a combination of the belt durability and the separation occurrence rate, and the smaller the value, the more excellent the durability.

Experimental Examples 1, 2, 6 and 8 are so-called comparative examples that do not satisfy the rubber physical properties specified in the present invention. Experimental Example 1 (Comparative Example 1) does not satisfy the Tan δ value, and Experimental Example 2
In Comparative Example 2, the value of E ′ exceeds the upper limit, and in Experimental Example 6 (Comparative Example 3), the value of Tan δ is not satisfied and E ′ is not satisfied.
Is an example in which the value of does not reach the lower limit, Experimental Example 8 (Comparative Example 4)
Is an example in which the value of Tan δ is not satisfied. Therefore, Experimental Examples 3, 4, 5, and 7 are Examples 1 to 4 of the present invention.

In each test, the experimental example 1 is standardized.
However, in Experimental Example 2 (Comparative Example 2) in which both Tan δ and E ′ were out of the specified conditions of the present invention, the separation was remarkably generated and the tire could not be put to practical use. In Experimental Example 6 (Comparative Example 3) in which both Tan δ and E ′ were deviated, almost no effect was recognized as compared with the standard. Further, in Experimental Example 8 (Comparative Example 4) where the condition of Tan δ was not satisfied, no effect was found.

Compared to these results, Tan δ and E '
Of Experimental Examples 3, 4, 5, which satisfy the conditions specified in the present invention,
In No. 7, the comprehensive evaluation is desirable, and especially E ′ is 1.5 × 10 ^{8 to} 3.5 × 10 ⁸ dyn / cm ^2.
The comprehensive evaluation is extremely high for the tires using the rubbers of Experimental Examples 4, 5, and 7 within the range of.

[0019]

INDUSTRIAL APPLICABILITY As described above, in the belt structure of a pneumatic radial tire, the present invention significantly enhances the durability of the belt by optimizing the physical properties of the rubber coating the steel cord. Further, the occurrence of separation at the belt end portion was small, and it was possible to provide a tire that is extremely useful in practice.

Claims (1)

[Claims] 1. A steel sheet having at least two layers, which is located between the tire carcass ply and the tread rubber and is arranged to intersect with the tire equatorial direction at an angle of 10 to 30 degrees.
In a pneumatic radial tire having a belt structure made of a rucor, the physical properties of the rubber coating the steel cord constituting the belt are Tan δ <E ′ × 3.9e ⁻¹⁰ +0.07, and 1.0 × 10 ⁸ dyn / cm ² <E ′ <4.0 × 10
A pneumatic radial tire having a characteristic of ⁸ dyn / cm ² .