JPH06191237A - Pneumatic radial tires - Google Patents

Abstract

PURPOSE:To provide a pneumatic radial tire improving maneuvering stability without lowering riding comfort and durability. CONSTITUTION:Sheet-like rubber reinforcing material 9 anisotropic in the modulus of elasticity is embedded in a position outside of an innermost side carcass 4a in a side wall part, with the direction large in the modulus of elasticity placed along the circumferential direction of a tire.

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 a pneumatic radial tire having improved steering stability without deteriorating riding comfort in a blistered tire having a low sectional height. .

[0002]

2. Description of the Related Art Conventionally, as means for improving the steering stability of a pneumatic radial tire, a reinforcing material such as steel cord or organic fiber cord such as nylon or aromatic polyamide is provided from the bead portion to the sidewall portion. Is being done. By inserting the reinforcing material in this way, the rigidity in the tire circumferential direction is increased and the steering stability during cornering is improved.

On the other hand, as the performance of vehicles has been improved in recent years, pneumatic radial tires with uneven hair have come to be used. Since the bulged pneumatic radial tire has a low cross-sectional height, embedding the cord reinforcing material also increases the rigidity in the tire radial direction, resulting in a significant reduction in riding comfort. Also, it becomes difficult to make adjustments to eliminate the rigidity step from the tread portion to the bead portion,
Separation easily occurs at the end of the cord reinforcing material, which causes a problem that the durability of the tire is significantly reduced.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic radial tire having improved steering stability without deteriorating riding comfort and durability.

[0005]

The present invention for achieving the above object provides a sheet-like rubber reinforcing material having anisotropy in elastic modulus at a position outside an innermost carcass in a sidewall portion. It is characterized in that a direction having a large elastic modulus is embedded along the tire circumferential direction. As described above, the rubber reinforcing material having anisotropy in elastic modulus is embedded so that the direction of the large elastic modulus is along the tire circumferential direction, so that the rigidity in the tire circumferential direction is increased and steering stability during cornering is improved. Can be improved. Further, since the direction having a small elastic modulus is arranged in the tire radial direction, the riding comfort is not deteriorated even in a tire having a low sectional height. Further, unlike the cord end of the cord reinforcing material, an extreme difference in rigidity does not occur, so that durability is not deteriorated.

An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an example of a pneumatic radial tire of the present invention. Reference numeral 1 is a tread portion, 2 is a bead portion, and 3 is a sidewall portion. The carcass is provided with two layers, an inner carcass 4a and an outer carcass 4b. Both ends of the inner carcass 4a are wound around the left and right bead cores 5 so as to be folded back from the tire inside to the outside. The outer carcass 4 b is wound around the bead filler 6 and the bead core 5. Further, a plurality of belt layers 7 are provided on the outer peripheral side of the tread portion 1 of the carcass 4a, 4b. A sheet-shaped rubber reinforcing material 9 is inserted between the outer side of the folded-back portion of the inner carcass 4a and the outer carcass 4b with a width H extending from the upper portion of the bead core 5 to the upper portion of the sidewall portion 3. Further outer carcass 4
The second bead filler 10 is provided on the outer side of b.

The rubber reinforcing material 9 is made of rubber having a large anisotropy in elastic modulus, and is arranged so that the direction having a large elastic modulus is along the tire circumferential direction. As such an anisotropic rubber, for example, a rubber compounded so that short fibers are arranged in one direction is preferably used. The short fibers are not particularly limited, but nylon, polyester, rayon, PVA, cotton, hemp, etc. can be used. The position of the rubber reinforcing material 9 is not particularly limited as long as it is outside the carcass located on the innermost side, but it is desirable to arrange it inside the outer carcass 4b.

The anisotropic elastic modulus of the rubber reinforcing material 9 is, as shown in FIG. 2, a tire circumferential elastic modulus a (kg / c).
It is preferable that m ² ) is a ≧ 30 kg / cm ² at 10% elongation, and is at least twice as large as the elastic modulus in the tire radial direction b (kg / cm ² ). As described above, the sidewall portion 3 is provided with the rubber reinforcing material 9 having anisotropy in elastic modulus.
By embedding the direction with a large elastic modulus along the tire circumferential direction, the rigidity in the tire circumferential direction is improved,
The elasticity in the tire circumferential direction at the time of cornering can be appropriately provided, and the steering stability at the time of cornering can be improved. In addition, since the rigidity does not increase significantly in the tire radial direction, the ride comfort is not reduced even with a tire having a low cross-sectional height, and separation with rubber occurs unlike conventional cord reinforcements. Does not reduce durability.

[0009]

[Examples] Tires 1 and 2 of the present invention and tires 1 and 2 of the present invention in which the tire size is 235 / 40ZR17 (having a cross-sectional height of 90.9 mm) in common and the constitution of the reinforcing material are different as follows are manufactured. did. Tire 1 of the present invention Tire structure: Fig. 1 Reinforcing material: Sheet-shaped rubber reinforcing material containing short nylon fibers Section width H = 55 mm Elastic modulus a = 115 kg / cm ² Elastic modulus b = 49 kg / cm ² Tire 2 of the present invention Tire structure : The position of the rubber reinforcing material 9 in FIG. 1 is replaced with the outer side of the outer carcass 4b. Reinforcing material: The same conventional tire 1 as the tire 1 of the present invention Tire structure: The tire without the cord reinforcing material 19 in FIG. 3 Conventional tire 2 Tire structure: Fig. 3 Reinforcement material: Reinforcement material made of steel cord Width H = 30 mm With respect to these four types of pneumatic radial tires, radial rigidity, circumferential rigidity, durability and weight were measured and evaluated under the following measurement conditions. The results shown in Table 1 were obtained. The evaluation values shown in Table 1 are represented by indexes with the measured value of Conventional Tire 1 being 100 (reference value).

Radial Rigidity A rim size of 17 × 8 and 1/2 JJ was mounted on the rim, air pressure of 2.3 kg / cm ² was filled, and a radial elastic modulus was measured when a load of 450 kgf was applied. Circumferential rigidity The circumferential elastic modulus was measured under the same conditions as the radial rigidity. Durability Up to 140% of maximum load, 13% load / 2 hours, then up to 270% load 13% / 4 hours. is there.

[0011]

[Table 1] As is clear from Table 1, since the tires 1 and 2 of the present invention have higher rigidity in the tire circumferential direction than the conventional tire 1 having no reinforcing material, the steering stability can be improved and the steel cords are made of steel cord. As compared with the conventional tire 2 having the reinforcing material, the tire radial direction rigidity is sufficiently small, and thus it is understood that the riding comfort is good. Also, the durability of conventional tire 1
It can be seen that it is about the same and the weight is not so large.

[0012]

As described above, according to the present invention, the rubber reinforcing material having anisotropy in elastic modulus is embedded so that the direction of the large elastic modulus is along the tire circumferential direction. It is possible to improve the steering stability during cornering. In addition, since the direction having the smaller elastic modulus is arranged in the tire radial direction, it is possible to maintain good riding comfort even in a tire having a low sectional height. Further, unlike the cord end of the cord reinforcing material, an extreme difference in rigidity does not occur, so that durability is not deteriorated.

[Brief description of drawings]

FIG. 1 is a half sectional view of a pneumatic radial tire of the present invention.

FIG. 2 is a perspective view showing a main part of a pneumatic radial tire of the present invention with a main portion cut away.

FIG. 3 is a half cross-sectional view of a conventional pneumatic radial tire.

[Explanation of symbols]

1 tread part 2 bead part 3 sidewall part 4a, 4b carcass 9 rubber reinforcing material

Claims (1)

[Claims] 1. A sheet-shaped rubber reinforcing material having anisotropy in elastic modulus is embedded at a position outside an innermost carcass in a sidewall portion in a direction having a large elastic modulus along a tire circumferential direction. Pneumatic radial tires.