JPH03213403A - Radial tire for travelling on sandy place - Google Patents

Abstract

PURPOSE:To improve durability and floating effect in low internal pressure travelling, by forming a belt cord out of organic fibers similar to those of a carcass cord while specifying the radius of curvature of surface in a tread section. CONSTITUTION:A tire 1 is provided with a carcass 6 extended from a tread section 5 to a side wall section 4 and folded back around a bead core 2 of a bead section 3. A belt layer 9 consisting of a plurality of plies 9A, 9B, having cords made of organic fibers similar to the carcass 6 and arranged at an angle of 17 deg.-34 deg. to the tire equator, is provided in the tread section 5 outside the carcass 6. The surface S of the tread section 5 has its center on the tire equator surface, which surface S are attached to a normal rim in the meridian surface including the tire axis when the tire is filled with the normal internal pressure. The surface S is also formed in an arc within the radius of curvature R of 150mm-350mm.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a radial tire for running on sandy terrain that has improved running performance on sandy terrain and improved durability.

[Conventional technology]

For example, in tires for sand buggies and other vehicles running on sandy terrain, in order to uniformly reduce ground pressure and enhance the floating effect, 1. Tires are often used at low internal pressures such as Oksc, and therefore, tires of this type generally have a bias structure that can maintain durability even at low internal pressures.

However, in recent years, as vehicles have increased in speed and performance, there has been a growing demand for improvements in steering stability and high-speed running performance on paved roads, and there is a strong desire to shift to a radial structure.

[Problem to be solved by the invention]

However, radial tires generally use a belt cord with a higher modulus than the carcass cord, usually a steel cord, to firmly tighten the carcass case.
The carcass crown becomes flat. Therefore, when such a tire is used at low internal pressure, the ground pressure at the tread shoulder increases unevenly compared to the ground pressure at the crown, causing uneven wear on the shoulder and causing a floating effect. and reduce traction performance.

Moreover, when used at low internal pressures, the amount of tread deformation when in contact with the ground and when not in contact with the ground increases, so a large amount of stress is concentrated at the end of the high modulus belt cord, causing ply open end separation between the carcass and the tire. Dramatically reduces durability.

The present invention is based on the fact that the belt cord is formed using the same low modulus organic fiber as the carcass cord, and an object of the present invention is to provide a radial tire for running on sandy terrain that can solve the above-mentioned problems.

[Means for Solving the Problems] In order to achieve the above object, the radial tire for running on sandy areas of the present invention has a radial tire for running on sandy roads, which is folded from the tread part through the sidewall part and around the bead core of the bead part, and also uses organic fibers. A carcass consisting of at least one carcass ply in which carcass cords are arranged in a radial manner, and a belt cord arranged on the outside of the carcass in the tire radial direction and inside the tread part and made of the same organic fiber as the carcass cord. 17 degrees or more and 34 degrees to the equator
a belt layer consisting of at least two belt plies arranged at an angle of less than The surface is formed by an arc having a center on the tire equatorial plane and having a radius of curvature R of 1501 mm or more and 350 mm or less.

Further, it is preferable that the organic fiber is nylon.

[Effect]

In the sandy radial tire of the present invention constructed as described above, the belt cord is formed using the same organic fiber as the carcass cord, eliminating the modulus difference between the two.
It is possible to suppress flattening of the carcass crown while appropriately increasing tread rigidity.

As a result, when running under low internal pressure, it is possible to maintain a feeling of ground contact while preventing the phenomenon of slumping, making safe driving possible. On the other hand, it is possible to equalize the ground pressure distribution, enhance the floating effect, and reduce uneven wear.

Moreover, since the belt cord can expand and contract along with the carcass when the tread deforms, stress concentration at the belt end can be alleviated.
It can reduce cord looseness and improve durability.

〔Example〕

An embodiment of the present invention will be described below based on the drawings.

FIG. 1 is a sectional view of the tire taken along a meridian plane that includes the tire axis.

In the figure, a radial tire 1 for running on sand (hereinafter referred to as tire 1) has a bead portion 3 through which a bead core 2 passes, a sidewall portion 4 extending outward in the tire radial direction from the bead portion 3, and a tread portion connecting the upper ends of the sidewall portion 4. 5 and
Also, between the bead portions 3 and 3, a carcass 6, which is obtained by folding both ends of the main body from the tread portion 5 through the sidewall portion 4 to the bead portion 3 around the bead core 2, is placed, and the tire is A belt layer 9 is wound on the radially outer side.

The carcass 6 includes one or more carcass cords, in this example two carcass cords arranged at an angle of 70 to 90 degrees with respect to the tire equator.
The folded ends of the carcass plies 6A and 6B, which are formed from two carcass plies 6A and 6B and are folded around the bead core 2 from the inside to the outside, terminate at different heights at the bead portion 3 or sidewall portion 4, respectively. ing.

Further, the carcass cord is made of, for example, nylon, polyester, rayon, etc. and has an initial elastic modulus of 150 to 1500.
Nylon cord, which is formed from an organic fiber cord having a weight of 1.5 kg/m'' and has particularly high strength and excellent fatigue resistance and moisture resistance, can be suitably used.

In addition, the belt layer 9 has the belt cord at a deeper angle than that of a normal radial tire, that is, 17 degrees with respect to the tire equator.
It is formed from two or more belt blazers 9A and 9B in this example arranged at an angle of 70 to 120% of the tread width and arranged at an angle of 34° or more and 34° or less. , will be arranged.

The belt plies 9A and 9B are arranged in different directions so that the belt cords intersect each other between the belt plies.

In the present invention, the belt cord is made of the same organic fiber as the carcass cord.

The purpose of this is to eliminate the difference in modulus between the belt cord and the carcass cord, which allows almost equal tension to be applied to both cords, reducing the feeling of stiffness and providing a moderate ground contact feeling, especially when running with low internal pressure. can be maintained, improving steering stability.

Furthermore, flattening of the carcass crown can be suppressed, and the ground pressure distribution can be made more uniform.

Moreover, since the belt cord can expand and contract together with the carcass during tread deformation when the tread is in contact with the ground or not in contact with the ground, stress concentration at the end of the belt can be alleviated and durability can be greatly improved.

Furthermore, when filled to the normal internal pressure, the tire rigidity can be increased in a well-balanced manner due to the uniform elongation of the belt cord and carcass cord, and the high steering stability and high-speed running performance characteristic of radial tires can be imparted.

In order to exhibit such tire performance, it is preferable that the surface S of the tread portion 5 is parallel to the crown contour of the carcass 6, that is, the tread cage thickness is approximately constant, and in particular, in order to improve the floating effect. When mounted on a regular rim and filled with regular internal pressure, the surface S must be formed into an arc having its center on the tire equatorial plane and having a radius of curvature R of 1501 or more and 350 mm or less.

〔Concrete example〕

A tire having the tire structure shown in FIG. 1 and a tire size of 900R158PH based on the specifications in Table 1 was manufactured as a prototype, and the floating performance, durability performance, and wear resistance performance of the trial tire were evaluated by actual vehicle tests.

The floating performance was evaluated by the running time when running a certain distance (50 m) on sandy ground under an internal pressure of 2.1 ksc, that is, the sandy start performance.
is expressed as an index with 100. Also, the durability performance is 1.0
The distance traveled until the belt breaks when the drum is run under an internal pressure of ksc is expressed as an index. The wear resistance is shown as the amount of wear when the actual vehicle is driven for 30,000 km on a general road under a specified internal pressure and a specified load, with Example product 2 set as 100.

The higher the value, the better.

〔Effect of the invention〕

In the radial tire for running on sandy roads of the present invention, the belt cord is made of the same organic fiber as the carcass cord, and the radius of curvature of the tread is restricted, so it has great durability when running at low internal pressure. It is possible to enhance the floating effect while improving the floating effect.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the present invention. 2...-bead core, 3--bead part, 4--sidewall part, 5... tread part, 6--carcass, 6A, 6B--carcass ply, -belt layer, 9A. B Belt braai, S-・-Surface.

Claims (1)

[Scope of Claims] 1. A carcass consisting of at least one carcass ply which is folded back from the tread portion through the sidewall portion and around the bead core of the bead portion, and in which carcass cords made of organic fibers are radially arranged; At least two belt cords arranged on the outside of the carcass in the tire radial direction and inside the tread portion, and made of the same organic fiber as the carcass cord, arranged at an angle of 17° or more and 34° or less with respect to the tire equator. and a belt layer consisting of a belt ply of A radial tire for running on sandy terrain formed by an arc having a radius of curvature R of 150 mm or more and 350 mm or less. 2. The radial tire for running on sandy soil according to claim 1, wherein the organic fiber is nylon.