JPS62128804A - Tire for all-ground vehicle - Google Patents

Abstract

PURPOSE:To improve the extent of steering stability, by specifying the ratio of a tire outer diameter to a mold outer diameter as well as the ratio of tire width to bead width at the time of filling normal internal pressure and a relationship between length of a bead apex and a tilt angle, respectively. CONSTITUTION:In case of a radial tire of 80 deg.-90 deg. in cord angles of carcass ply 3, a ratio Dt/Dm between a tire outer diameter Dt and a mold outer diameter Dm at the time of filling normal internal pressure should be set to a range of 1.0-1.05. Also, a ratio Wt/Wb between tier width Wt and bead width Wb should be set to a range of 1.2-1.4. In addition, length l of a bead apex 4 and angle theta made by a straight line passing through a bottom part B and an upper end E of the apex 4 and a line RL passing through the bottom part B and paralleling a tire rotation axis are constituted so as to satisfy the specified relation. With this constitution, steering stability is improvable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an all-terrain vehicle tire that is suitable for running on all types of terrain such as sand, mud, landings, etc. and has improved ride comfort and t% longitudinal stability.

[Conventional technology]

Conventionally, the wheels mounted on all-terrain vehicles have not been equipped with suspensions, so in order to improve the ride comfort of this type of vehicle, it is necessary for the tires to absorb shock from the road surface when driving. There is. Therefore, as the structure of tires mounted on this type of vehicle, a radial or semi-radial structure that does not use a bell) 75 is adopted, and an internal pressure of about 0.2 kff/- is used. However, this type of tire generally has poor handling stability due to the above-mentioned structure, and in order to improve the handling stability, it is effective to increase the Fi rigidity of the tire. For this reason, a method is adopted in which the tire has a flat profile and the flex zone on the side part is reduced.

[Problem that the invention seeks to solve]

However, when a tire with a flat profile is filled with an inner core, the flat profile changes to the normal profile (
(natural equilibrium shape), that is, the outer diameter of the tire increases, and a particularly large tensile strain occurs in the crown portion of the tire. As a result, tire cracks occur due to repeated use, leading to tire damage.

Therefore, the present invention relates to a tire for an all-terrain vehicle that does not use a belt layer and has improved riding comfort and handling stability without causing the above-mentioned problems.

[Means for solving problems]

In the present invention, the cord is set at an angle of 80° to 90° with respect to the tire circumferential direction.
In an all-terrain vehicle tire comprising a carcass in which both ends of plies arranged at an angle of ゛ are folded back around a bead core, and a bead apex extending from the upper side of the bead core in the direction of the sidewall, <8) Tire when filled with normal internal pressure. Outer diameter 1) The ratio of t to mold outer diameter Dm, Dt/Dm, is in the range of 1.0 to 1.05, and the ratio of tire width Wt to bead width persimmon/Wb is 1.2 to 1. .4, and (b) the length l of the bead apex and the bead inclination angle θ of the bead apex with respect to the tire rotation axis direction satisfy the relationship o, ttvt≦1cosθ≦0.2−t. all terrain vehicle.

It is a tire for use.

An embodiment of the present invention will be described in detail below with reference to the drawings.

In the figure, a tire 1 includes a carcass 3 whose both ends are folded back around a bead core 2 and locked, and a folded portion 3 of the carcass 3.
a and the base of the carcass 3. Here, the ply cord of carcass 3 is 80° to 90° with respect to the tire circumferential direction.
It is a so-called radial structure, or semi-radial structure, which is arranged in degrees. And the ply of carcass 3 is usually 1
~3 pieces are used, both ends of which are folded back and locked in opposite directions from the inside or outside of the bead core, preferably ending beyond the upper end of the bead apex 4. Further, the carcass cord may be a fiber cord of nylon, polyester, rayon, or aramid.

Also, tire outer diameter Dt and mold outer diameter On when filling with regular internal pressure
The ratio of Dt/D to + is in the range of 1.0 to 1.05.

-Finally, if the aspect ratio of a tire without a belt layer is increased, the outer diameter of the tire when filled with the normal internal pressure will be larger than the outer diameter of the tire in the mold, and the difference will be particularly noticeable at the tire crown. This is because the tire deforms into a natural equilibrium shape when the internal pressure is filled, and tensile strain becomes particularly large at the crown portion. Therefore, the present invention aims to flatten the tire and suppress the above-mentioned tensile strain during internal pressure filling to a minimum. That is, Dt/
If DL1 exceeds 1.05, distortion at the tire crown will be large as described above, and cracks and scratches will easily occur during use of the tire, which is not preferable. Naori t/Dm can be set within this range by adjusting the rubber thickness of the tread crown or the bead apex as described below.

Also, the ratio of the tire width t to the bead width Wb, Wt/Wb, is 1.
It is in the range of 2 to 1.4. This is to maintain the ride comfort and lateral rigidity of the tire as well as the arrangement of the bead apex 4, which will be described later.If it is smaller than 1.2, the ride comfort will be poor;
lateral stability is not maintained sufficiently. Here, the bead width is defined as the distance between the point P where the rim flanges on both sides start contacting the bead portion of the tire.

Next, in order to maintain high lateral rigidity, that is, lateral stability of the tire, the arrangement of the bead apex 4 and the bead width are set within a specific range. In other words, the bottom B of bead apex 4
The length l of the bead apex 4 defined as the straight line length from to its upper end E, and the bottom B of the bead apex 4
The bead inclination angle θ defined by -ζ is O, IWt5βcoSθ≦0 by the angle between the straight line extending through the upper JE and the line RL passing through the bottom L3 and parallel to the concave rotation axis.
．． It is necessary to satisfy the following relationship. Here lcosθ<0. For IWT, bead apex 4
This means that the length l is short or the bead inclination angle θ is large, which reduces the lateral rigidity of the tire and reduces the ride comfort. On the other hand, when Acosθ>0.2 W t, the longitudinal stiffness becomes too high and the riding comfort deteriorates. Therefore, by setting 1 cos θ within the above range, it becomes possible to simultaneously satisfy the characteristics of ride comfort and lateral rigidity.

The JISA hardness of Bead Apex 4 is 85°.
It is preferable that it is above. If the hardness of the bead apex 4 is insufficient, it will be difficult to flatten the tire as described above, and the lateral rigidity will be insufficient, which is unfavorable in terms of handling stability.

〔Effect of the invention〕

As mentioned above, the present invention has a tire outer diameter of 0 when filled with the normal internal pressure.
The ratio Dt/DI11 of 1 and the mold outer diameter Dm is specified within a predetermined range to suppress tensile strain during internal pressure filling, and furthermore, the bead width,
Since the bead apex is arranged within a specific range, ride comfort and handling stability can be further improved.

[Brief explanation of drawings]

FIG. 1 shows a sectional view of the tire of the present invention. 1-tire, 2-bead core, 3-carcass, 4-bead apex.

Claims (2)

[Claims] (1) A carcass in which both ends of plies in which cords are arranged at an angle of 80° to 90° with respect to the tire circumferential direction are folded back around a bead core, and a bead apex extending from the upper side of the bead core toward the sidewall. In tires for terrain vehicles, (a) the ratio of the tire outer diameter Dt to the mold outer diameter Dm when filled with normal internal pressure, Dt/Dm is 1.0
-1.05, and the ratio Wt/Wb of the tire width Wt and bead width Wb at that time is 1.2 to 1.4, and (b) the length l of the bead apex and the bead apex Bead inclination angle θ with respect to the tire rotational axis direction
An all-terrain vehicle tire, characterized in that satisfies the relationship 0.1Wt≦lcosθ≦0.2Wt. (2) The all-terrain vehicle tire according to claim 1, wherein the bead apex has a JISA hardness of 85° or more.