JPH04154404A - Radial tire having belt reinforcement layer - Google Patents

Abstract

PURPOSE:To effectively prevent a belt from being separated from a carcass due to centrifugal force at the time of a high speed rotation of a tire by arranging a cord of the high Young's modulus for belt reinforcement at a belt end portion where a free end of a belt cord is positioned. CONSTITUTION:A radial tire 10 is provided with a belt 16 whose outside surface is covered by a cap ply 18 between a carcass 12 and a tread 14. The CAP ply 18 is formed of three ribbons 24, 26, 28 consisted of plural rubber coated parallel lined cords. The ribbon 24 of the three ribbons is spirally wound at the central portion excluding both end portions in the cap ply 18. In this case, the ribbon 24 is provided with a cord made of thermal contractive fiber such as nylon fiber. The ribbons 26, 28 arranged on both sides of the cap ply 18 are provided with a cord made of the Aramid fiber or a cord made of high elastic modulus fiber such as a curled wire cord.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a radial tire having a belt reinforcement layer. Specifically, a belt and a cap ply having cords for reinforcing the belt arranged in the circumferential direction of the tire to cover the entire width of the belt are arranged on the carcass, or the belt and the cap ply are arranged on the carcass. In addition, there is an edge ply in which reinforcing cords are arranged in the circumferential direction of the tire and placed at the end area of the belt, and the cap ply and edge ply are made by arranging multiple cords extending in the circumferential direction of the tire in parallel. This invention relates to a radial tire made of a spirally wound ribbon.

[Prior Art] In a radial tire, the free end of the belt cord is located at the end of the belt, so when the tire rotates at high speed, the belt end tends to separate from the carcass due to centrifugal force. To prevent this, place a cap ply or a cap ply and an edge ply on the
Ru.

The cords constituting the cap ply and the edge ply are made of heat-shrinkable fibers such as nylon. This is because the cord is heat-shrinked during vulcanization and the belt is tightly tightened.

[Problems to be Solved by the Invention] In general, this type of cord has a thermal shrinkage rate of 2.7 g/d when heated in air at a temperature of 150'C for 3 minutes by changing the heating conditions, etc. Time elongation rate (%
), the sum of the thermal shrinkage rate (%) and the elongation rate (%) under a load of 27 g/d remains almost constant. The heat shrinkage rate indicates how much the product shrinks when heated; if a small amount of heat is applied to cause partial shrinkage, the remaining heat shrinkage rate will decrease, and the constant load elongation rate will increase accordingly. Become.

Therefore, thermal contraction occurs during actual vulcanization, and the elongation rate after vulcanization increases accordingly. The cap ply is formed in a flat state, and during vulcanization it is shaped into an ellipsoid shape that corresponds to the cross-sectional shape of the tire circumferential surface, so the relatively small diameter end or edge ply of the cap ply is subject to heat shrinkage. is large, and as a result, it is easy to stretch, and the belt tightening force at the end or edge ply of the cap ply is small. Therefore, separation of the belt ends as described above cannot be effectively prevented.

Additionally, heat-shrinkable fibers are relatively thermoplastic. Therefore, when the internal temperature of the tire increases significantly during high-speed running, the belt tightening effect at the end of the cap ply further decreases, and the high-speed durability becomes even more insufficient.

[Means for Solving the Problems] In order to solve the above problems, in the present invention, in the radial tire mentioned at the beginning, when the cord reinforcing layer consists of only the cap ply, the width of the cap ply is A cord made of heat-shrinkable fibers was placed in the center, and a cord made of high Young's modulus fibers was placed at the ends of the cap ply. Further, when the cord reinforcing layer is composed of a cap ply and an edge ply, a cord made of heat-shrinkable fibers is placed on the cap ply, and a cord made of high Young's modulus fiber is placed on the edge ply.

[Function] A belt reinforcing cord with a high Young's modulus is placed at the end of the belt where the free end of the Kobelt cord is located, which effectively prevents the belt from separating from the carcass due to centrifugal force when the tire rotates at high speed. .

Although the high Young's modulus cord has low thermoplasticity, this is not a problem because the extent to which the belt side end expands in diameter due to vulcanization is small.

Further, the heat-shrinkable cord arranged in the center of the belt reinforcing layer has relatively high thermoplasticity and can be easily expanded in diameter by vulcanization, so that the uniformity of the tire is not lost during vulcanization.

In addition, Japan Rubber Association Journal Vol. 51 No. 3 No. 152-168
The page shows a formula for calculating the distribution of the tensile membrane force in the circumferential direction of the belt, but when calculating the membrane force using this formula, it is found that between the edge of the belt and a point about 15 meters from the edge of the belt, There is a drop in membrane strength. Therefore, in a belt consisting of a plurality of flies, it is preferable that at least the outermost 5 was of the wide end of the fly be reinforced with cords having a high Young's modulus.

[Embodiment] First Embodiment FIGS. 1 and 2 show an embodiment of the radial tire of the present invention.

This radial tire 10 has a carcass 12 and a tread 1.
4, there is a belt 16 whose outer surface is covered with a cap ply 8.

The belt 16 consists of two layers: a first belt blazer 2o and a second belt blazer 22 having a narrower width. The angle of the steel cords in each braai 20.22 to the tire equator is 15-30'' and intersect each other.

The cap ply 18 on the belt 16 consists of three ribbons 24, 28, made of rubberized cords arranged in parallel.
28.

Of these three ribbons, the ribbon 24 is spirally wound around the center of the cap ply excluding both ends. This ribbon 24 has a cord made of heat-shrinkable fibers such as nylon. Young's modulus of nylon fiber is 3
00 kg/wava2. Cap ply 18
The cords included in the ribbons 28 and 28 arranged on both sides of the cord are cords made of aramid fibers or cords made of fibers with high elastic modulus such as curled wire cords.

The Young's modulus of the aramid fiber is 4300 kg/mlI2.

Second example 3 and 4 show a second embodiment of the invention.

This embodiment differs from the first embodiment in that edge plies 30, 32 are provided to cover both ends of the cap ply. The cap ply 18 is formed by winding a ribbon 24 having a cord made of heat-shrinkable fiber such as nylon in a spiral manner over its entire width. Engineering/Sojibli 30
．． 32 is a ribbon 34, 38 made of cords made of aramid fibers or high Young's modulus fiber cords such as curled wire cords, both of which are spirally wound.

Comparative Example 'W' A tire having the same structure as the tire shown in Figure 3, but with nylon cords inserted over the entire surface of both the cap ply and the edge ply, was prepared as a comparative example.

The tires of Example 1.2 and Comparative Example were tested under the high-speed durability test conditions stipulated in the European Economic Commission Regulation ECE30, and after passing the specified conditions, the tires were run in increments of 10 km/h every 20 minutes until they broke. continued. In Table 1, the required time is expressed as an index with the tire of the comparative example set as 100.

From the above results, compared to the comparative example, Example 1 of the present invention
It can be seen that high-speed durability is significantly improved in both cases.

[Effect of the invention] By disposing a belt reinforcing cord with a high Young's modulus at the belt end where the free end of the belt cord is located,
It is possible to effectively prevent the belt from separating from the carcass due to centrifugal force when the tire rotates at high speed.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a radial tire having a belt reinforcing layer according to an embodiment of the present invention, FIG. 2 is a schematic diagram showing the overlapping state of each layer in the previous embodiment, and FIG. FIG. 4 is a schematic diagram showing the overlapping state of each layer in the previous example. [Description of symbols 12... Carcass 16... Belt 18... Cap ply 24.26.28... Ribbon 30.32 constituting the cap ply・・・・・・Engraving of edge ply drawing (no change in content) Figure 1 Figure 2 Figure 3 @4g1 Procedural amendment (,5E) January 24, 1991

Claims (1)

[Claims] 1. A radial tire comprising, between a carcass and a tread, a belt and a cap ply in which a ribbon having a plurality of parallel cords is spirally wound to cover the belt, the cap ply A radial tire characterized in that a cord made of heat-shrinkable fiber is arranged at the center of the width, and a cord made of high Young's modulus fiber is arranged at the end of the cap ply. 2. Between the carcass and the tread, a belt, a cap ply that covers the belt by spirally winding a ribbon with multiple cords in parallel, and a ribbon with multiple cords in a spiral spiral. In this radial tire, the cap ply has a cord made of heat-shrinkable fiber, and the edge ply has a cord made of high Young's modulus fiber. A radial tire characterized by: