JP3422555B2 - Pneumatic 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 tire which can be suitably used especially as a tire for heavy-duty vehicles and which can improve steering stability while maintaining durability and reduce the weight of the tire.

[0002]

2. Description of the Related Art In recent years, as a part of the improvement of the global environment, energy saving has been demanded, and in automobiles, tires are used in order to save fuel consumption and to reduce the total weight of the vehicle to increase the load. Reducing the weight of itself is an important issue.

In a pneumatic tire, a bead apex is provided in the bead portion in order to maintain the vertical rigidity of the tire and increase the lateral rigidity. Especially for heavy-duty tires such as trucks and buses, in order to obtain higher lateral rigidity, it has been conventionally practiced to use hard rubber for the bead apex and to increase its volume. It was a cause of hindering the change. Therefore, in recent years, in order to reduce the weight of the bead apex, it is desired to make the bead apex into a hollow structure having a plurality of holes, for example, in Japanese Patent Laid-Open Nos.
It is proposed by Japanese Patent Publication No. 95513.

[0004]

However, in the above-mentioned proposal, since the directions of the holes provided in the bead apex are arranged in the tire axial direction, the opening ends of the holes come into contact with the carcass or the sidewall rubber, When a green tire is vulcanized and molded, in a carcass, its topping rubber tends to penetrate into the holes of the bead apex, and as a result, the carcass cords are exposed and the cords are damaged. In addition, as a result of the presence of air in the holes of the bead apex, the air expands due to the temperature rise due to the use of the tire, and the durability of the bead apex itself is impaired.

The present invention is based on the fact that the bead apex contains an inorganic hollow filler, and it is possible to achieve weight reduction without reducing the volume of the bead apex, while maintaining durability, and by the reinforcing effect of the hollow filler. It is an object of the present invention to provide a pneumatic tire capable of enhancing lateral rigidity of a tire and improving steering stability.

[0006]

The invention according to claim 1 of the present application provides a carcass in which a folded-back portion that is folded back around the bead core is provided in the main body portion from the tread portion to the bead core of the bead portion through the sidewall portion. , A belt layer arranged radially outside of this carcass and inside the tread portion,
The tire has a tire cross-section height of 0.4 that extends from the bead core in the radial direction and passes between the carcass main body portion and the folded portion.
〜0.5 times bead apex and
The bead apex has an inorganic and fine hollow hollow filler in a rubber substrate, the volume ratio of which is
The hollow filler has a particle diameter of 5 to 3000 μm and a bulk specific gravity of 0.06 to 0.40, which is formed by using a filler mixed rubber mixed in a ratio of 20 to 30 with respect to the rubber substrate 100. It is a pneumatic tire characterized by that.

The bead portion has an inner surface, a bottom surface, and
The clinche pex that covers the outer surface is arranged and the bead
A cord reinforcement layer that wraps around the carcass by folding around
It is characterized by comprising .

[0008]

The bead apex is formed by using the compounded rubber in which the inorganic hollow filler is mixed in the rubber substrate. As the inorganic hollow filler, for example, shirasu balloons, pearlite, fly ash balloons and the like using natural raw materials, and glass balloons, alumina bubbles and the like using artificial raw materials are generally known and form fine hollow spheres. Therefore, the compressive strength and rigidity of the compounded rubber is increased by the reinforcing effect of this hollow filler, and the lateral rigidity of the tire can be increased compared to the conventional bead apex formed of hard rubber in a solid (lump) shape, and steering stability can be improved. Can be improved.

Further, since the specific gravity of the compounded rubber is reduced by mixing the hollow filler, the weight reduction of the bead apex can be achieved. By increasing the compressive strength, the volume of the bead apex can be reduced,
In such a case, further weight reduction is promoted.

Further, since the air inside the hollow filler is sealed in a shell shape by the inorganic material, damage to the bead apex due to temperature rise can be suppressed and durability can be maintained.

By selecting the particle size and mixing ratio of the hollow filler, it becomes possible to adjust and set the longitudinal rigidity and lateral rigidity of the tire without changing the basic dimensions of the tire. It can be adapted to diversification of performance.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a pneumatic tire 1 has a sidewall portion 3 extending inward in the radial direction from both ends of a tread portion 2 and a bead portion 4 located at the radially inner end of the sidewall portion 3. In this example, it is formed as a heavy duty radial tire. Also, for the pneumatic tire 1,
A carcass 6 is bridged between the bead portions 4 and 4, and a belt layer 7 is wound on the outside of the carcass 6 in the radial direction and inside the tread portion 2.

The carcass 6 has a toroidal main body portion 6A that passes through the tread portion 2 and the sidewall portion 3 and reaches the bead core 5 of the bead portion 4, and is connected to both ends of the toroidal body portion 6A from the inside of the tire to the outside of the tire. A bead apex 9 is provided between the main body 6A and the folded-back portion 6B.

The carcass 6 comprises one or more carcass plies in which carcass cords are arranged at an angle of 70 to 90 ° with respect to the tire equator C in this embodiment, and in this embodiment, one carcass ply. In this example, a steel cord is preferably used as the cord. Organic fiber cords such as nylon, rayon, polyester and aromatic polyamide may be used depending on the required tire performance.

The belt layer 7 is composed of a plurality of high-strength belt cords arranged at an angle of 10 to 70 ° with respect to the tire equator C. In this example, the belt layer 7 is arranged in order from the carcass 6 side. -It consists of 4th belt ply 7a-7d.
The maximum width of the belt layer 7, that is, the widest ply width WB of the second belt ply 7b is the width W of the tread portion 2.
T is 0.80 to 0.95 times, and it is preferable to reinforce over a wide range of the tread portion 2. Belt ply 7a-7d
At least two of them, in this example, the second to fourth belt plies 7b to 7d have a cord angle with respect to the tire equator C of 10 to 25 degrees, for example, a shallow angle of 16 degrees, and the cords intersect each other between the plies. Arrange in the direction you want. Further, the first belt ply 7a is provided with the carcass 6 by tilting the cord angle at a deep angle of 40 to 70 degrees, for example 67 degrees.
The rigidity difference between the tread portion 2 and the tread portion 2 is improved by forming a strong triangle structure together with other belt cords. In this example, steel cord can be used as belt cord, but nylon,
Organic fiber cords such as rayon, polyester and aromatic polyamide may also be used. The belt layer 7 may be formed of first to third belt plies 7a to 7c.

The bead apex 9 has a triangular cross section which extends from the bead core 5 outward in the radial direction of the tire, and has a radially outer end P in this embodiment.
The bead apex height HB, which is the height from the bead base line L, is 0.40 to 0.5 of the tire cross-sectional height H.
The height is increased to 0 times, and the bead portion 4 to the sidewall portion 3 are reinforced. Further, the height HC of the folded-back portion 6B of the carcass 6 from the bead base line L is formed as a so-called low turn-up which is set smaller than the bead apex height HB. That is, since the folded-back portion 6B terminates at the side surface portion of the bead apex 9, the concentration of bending stress can be relieved and the ply end peeling can be prevented.

The bead apex 9 is formed by using a filler mixed rubber in which an inorganic hollow filler is mixed in a rubber substrate.

The hollow filler is a fine spherical hollow body having a shell structure, and in the present application, natural raw materials such as shirasu, pearlite and obsidian, or sodium borosilicate, alumina and the like. An inorganic material using an artificial raw material is used. Known natural materials include so-called shirasu balloon, pearlite and fly ash balloons, and artificial materials include so-called glass balloons and alumina bubbles.

Since such an inorganic hollow filler has high compression / tensile strength and rigidity despite having a low bulk specific gravity, it effectively reinforces the rubber mixed with filler to increase the rigidity of the bead apex 9 and Weight can be reduced. In this example, the volume (volume) of the bead apex 9 is reduced by about 10% as compared with the conventional bead apex made of hard rubber due to the reinforcing effect.

The hollow filler has a particle size of 5 to 5.
Those having a bulk specific gravity of 3000 μm and a bulk specific gravity of 0.06 to 0.40 can be preferably used. It is difficult to obtain ultra-fine particles with a particle size smaller than 5 μm,
The larger one, when mixed in the rubber substrate, may impair the strength of the rubber, particularly the cut resistance. When the bulk specific gravity is less than 0.06, the hollow filler itself is inferior in strength because the hollow ratio becomes excessive, and when it is more than 0.40, the weight reduction cannot be sufficiently achieved.

In the hollow filler, it is preferable to mix the volume ratio of the hollow filler with the rubber base in a ratio of 20 to 30, preferably about 25, in order to balance the reinforcing effect and the weight reduction. Desirably, at this time, the specific gravity of the bead apex 9 itself can be reduced by about 12 to 13%.

As the rubber base of the filler mixed rubber, conventional rubber for bead apex such as natural rubber (NR) and synthetic natural rubber (IR) can be used.

The bead portion 4 is provided with a clinche pex 10 for covering the inner side surface, the bottom surface, and the outer side surface of the bead portion 4 so as to prevent damage such as rim displacement, and the bead core 5 is folded back. A cord reinforcing layer 11 is provided so as to surround the carcass 6. The clinche pex 10 is made of relatively hard rubber having excellent wear resistance, and has a clinche pex height from the bead base line L on the outer side which rises radially outward from the bottom surface of the bead along the rim flange. HD exceeds the height of the rim flange and is set smaller than the bead apex height HB. The cord reinforcing layer 11 is, for example, a high-strength cord array ply made of steel or the like, and has the folded portion 6B.
Has a height smaller than the height HC of the carcass 6 and prevents the carcass 6 from being damaged around the bead core 5.

(Specific Example) A tire having a tire size of 225R22.5T / L having the structure shown in FIG. 1 was prototyped based on the specifications shown in Table 1, and the weight of the prototype tire was compared with that of a conventional tire.

[0025]

[Table 1]

[0026]

Since the pneumatic tire of the present invention is constructed as described above, it is possible to improve steering stability while maintaining durability and achieve weight reduction.

[Brief description of drawings]

FIG. 1 is a meridian sectional view of a tire showing an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a bead portion.

[Explanation of symbols] 2 tread section 3 Side wall part 4 bead section 5 bead core 6 carcass 6A main body 6B Folding part 7 Belt layer 9 bead apex

Claims (2)

(57) [Claims] 1. A carcass provided with a folded-back portion for folding back around the bead core in a main body portion extending from a tread portion to a bead core of a bead portion through a sidewall portion, and a carcass arranged radially outside and inside the tread portion. Cross section of the belt layer, which extends between the body portion of the carcass and the folded portion and extends radially from the bead core.
0.4 to 0.5 times the bead apex, and the bead apex has a volume ratio of the inorganic and fine hollow hollow filler in the rubber base to the rubber base,
The hollow filler has a particle diameter of 5 to 3000 μm and a bulk specific gravity of 0.06 to 0.40, which is formed by using a filler mixed rubber mixed in a ratio of 20 to 30 with respect to the rubber substrate 100. A pneumatic tire characterized by the following. 2. The bead portion includes an inner side surface, a bottom surface, and
The clinche pex that covers the outer surface is arranged and the bead
A cord reinforcement layer that wraps around the carcass by folding around
The pneumatic tire according to claim 1 , further comprising: