JP2713729B2 - Pneumatic radial tire for heavy loads - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a heavy-duty pneumatic radial tire for trucks or buses, and particularly to a technique for improving the durability of a bead portion.

(Prior Art) Since heavy load tires are indispensable for heavy load resistance, the bead portion has a turn-up ply structure having a folded portion in which a carcass ply is wound around the bead core from the inside to the outside of the tire.

Since this kind of tire is used under heavy load, the rubber and cord will peel off the outside of the chafer when the chafer is provided outside the ply turn-up part or as a reinforcing material in the bead part, making it unusable Often becomes.

Conventionally, techniques for improving the adhesion between the rubber and the cord or improving the quality of the rubber have been known for the separation between the rubber and the cord, but no means for improving the structure of the tire is known.

(Problems to be Solved by the Invention) Therefore, in the present invention, there is an object that achieves prevention of separation of rubber and cord in a bead portion by improving a bead portion structure, thereby improving the durability of the bead portion.

(Means for Solving the Problems) The present invention comprises a ply in which cords arranged in parallel to each other are arranged in a direction perpendicular to the equatorial plane of the tire, and at least one ply is formed around a pair of bead cores from the inside of the tire. A pneumatic radial tire having a toroidal carcass, which is a turn-up ply having a folded portion that is turned outward, is parallel to the tire rotation axis in a tire radial section in a state where the tire is mounted on a regular rim and filled with a regular internal pressure. The ply body portion and the folded portion of the turn-up ply in a region sandwiched between the tangent line of the rim flange forming the rim flange and the parallel line separated from the tangent line to the tire tread side by 2/3 times the rim flange height, Arranged in parallel so that the shear deformation occurring in the region becomes uniform, and having a rubber layer between the ply body portion and the folded portion in the region, It consists of a pneumatic radial tire for heavy loads, characterized in that the thickness of the rubber layer is within 0.58 times the bead core diameter, and a ply in which cords arranged in parallel to each other are arranged in a direction perpendicular to the equatorial plane of the tire. At least one ply is provided with a toroidal carcass which is a turn-up ply having a folded portion wound around the pair of bead cores from the inside to the outside of the tire, and a chafer arranged outside the tire at the folded portion. In a radial tire, in a tire radial cross section in a state where the tire is mounted on a regular rim and filled with a regular internal pressure, a tangent line of a rim flange parallel to a tire rotation axis and a rim flange height from the tangent line to a tire tread side by 2 / The ply body portion and the folded portion of the turn-up ply are formed in the region sandwiched by the parallel lines separated by 3 times in the region. Arranged in parallel so that the shear deformation becomes uniform, and having a rubber layer between the ply body portion and the folded portion in the region, the thickness of the rubber layer is within 0.58 times the bead core diameter, A pneumatic radial tire for heavy loads, characterized in that wedge rubber is disposed between a turn-back portion and a chafer. It is.

The "regular rim" mentioned here is JATMA YEAR BOOK
(1988 version).

The “regular internal pressure” refers to the air pressure corresponding to the maximum load in the applicable size and ply rating of the tire described in JATMA YEAR BOOK (1988 edition).

Further, "bead core diameter" is, when imagining a straight line that passes through the center of the bead core and is parallel to the tire rotation axis in the tire radial cross section, the shortest distance l between intersections of this straight line and the cross-sectional contour of the bead core is defined as means.

FIG. 1 illustrates the structure of a bead portion of a pneumatic radial tire for heavy load according to the present invention.

In the figure, 1 is a carcass made of a turn-up ply, 2 is a folded portion of the ply, 3 is a chafer for reinforcing the outside of the folded portion 2, 4 is a bead core, and 5 is a rim flange.

The carcass 1 has a rim flange 5 parallel to the tire rotation axis.
In a region sandwiched between a tangent line m and a parallel line n separated by 2/3 times the height of the rim flange, the ply body and the folded portion 2 are substantially parallel (d ₁ ≒ d ₂ ), In addition, the interval is set within 0.60 times the diameter l of the bead core 4 (d ₁ ≦ 0.60 l).

FIGS. 2A to 2C show another bead portion structure according to the present invention. In any of the examples, the carcass has a distance d ₁ dd ₂ between the ply main portion and the folded portion in a region sandwiched between the tangent m and the parallel line n and d ₁ ≦ 0.60.
Needless to say, it is arranged at l.

The example of the figure shows that wedge rubber 6 is disposed between the folded part 2 of the ply and the chafer 3, and the figure (b) shows an example in which the end of the folded part 2 is extended to the tire tread side, and FIG. 3C shows an example in which the chafer has a two-layer structure of 3a and 3b, and one of the chafers 3a is extended from the bead core to the inside of the tire.

Here, the wedge rubber 6 is a tire having a rim flange height of 1/3 times from the straight line parallel to the tire rotation axis passing through the maximum width position of the bead core and the tangent of the rim flange parallel to the tire rotation axis to the tire tret side. It is desirable to arrange it in a range between two straight lines, a straight line parallel to the rotation axis and a straight line.

(Operation) The destruction phenomenon that leads to the separation of rubber and cord in the bead portion is caused by shear strain in the radial cross section of the tire when the tire rolls, and this shear strain causes the bead portion to shear in the cross section when the tire rolls. Research has shown that it can be caused by deformation.

On the other hand, the tire according to the present invention arranges the ply body and the folded part in parallel particularly in the bead part,
The distance d ₁ between the turn-back part and the ply body part is 0.
By setting it within 58 times, the deformation at the time of rolling of the bead portion can be changed from shear deformation to bending deformation. Therefore, the shear strain generated at the rim-side interface of the folded portion of the ply can be reduced, and the separation between the rubber and the cord can be suppressed.

Another reason for disposing the ply body portion and the folded portion in the bead portion in parallel is to make the shear deformation in such a failure area uniform and not to concentrate the shear deformation in a part.

To avoid the disadvantage that so-called rubber flow occurs in the kettle during vulcanization in the tire manufacturing process due to manufacturing benefits, a chafer is arranged outside the folded portion of the ply, and the chafer and the folded portion are further arranged. It is effective to arrange a wedge rubber between them. That is, the rubber flow between the chafer and the folded portion is sealed, so that the folded portion and the ply body can be arranged in parallel, so that the so-called gouging of the bead portion can be easily realized.

(Example) For size 10, 00R20, heavy load tires having a radial structure carcass using a ply made of steel cord were manufactured with a bead portion having a structure shown in FIGS. In the running of the ply, measured the running distance until the peeling of the rubber from the folded part of the ply or chafer, and the result is shown in the attached table as an index when the conventional tire to which the structure of FIG. Show. The distance d ₁ , d ₂ between the folded portion and the ply and the bead core diameter 1 in each tire are also shown in the following table.

(Effects of the Invention) According to the present invention, it is possible to improve and improve the durability of a bead portion required for a heavy-load pneumatic radial tire used for trucks and buses, particularly under load.

[Brief description of the drawings]

1 and 2 (a) to 2 (c) are sectional views showing a bead portion structure according to the present invention, and FIG. 3 is a sectional view of a conventional bead portion. 1 ... carcass 2 ... folded part 3 ... chafer 4 ... bead core 5 ... rim flange 6 ... wedge rubber

Claims (2)

(57) [Claims] 1. A ply in which cords arranged in parallel to each other are arranged in a direction perpendicular to an equatorial plane of a tire, and at least one ply has a folded portion wound around the pair of bead cores from the inside to the outside of the tire. A pneumatic radial tire having a toroidal carcass that is a turn-up ply having a tangential line of a rim flange parallel to the tire rotation axis in a tire radial cross section in a state where the tire is mounted on a regular rim and filled with a regular internal pressure. From the tangent line to the tire tread side, the ply main body and the folded portion of the turn-up ply in the region sandwiched by the parallel line separated by 2/3 times the rim flange height from the tang flange side, the shear deformation occurring in the region is uniform And a rubber layer between the ply body portion and the folded portion in the region, and a thickness of the rubber layer is set to bead core. Heavy duty pneumatic radial tire characterized by being within 0.58 times. 2. A ply in which cords arranged in parallel with each other are arranged in a direction perpendicular to the equatorial plane of the tire, and at least one ply has a folded portion wound around the pair of bead cores from the inside to the outside of the tire. A pneumatic radial tire having a toroidal carcass, which is a turn-up ply having, and a chafer arranged outside the tire at the turn-back portion, in a tire radial section in a state where the tire is mounted on a regular rim and filled with a regular internal pressure, The ply body of the turn-up ply is folded back in the area between the tangent line of the rim flange parallel to the tire rotation axis and the parallel line separated by 2/3 times the rim flange height from the tangent line to the tire tread side. And the parts are arranged in parallel so that the shear deformation occurring in the region becomes uniform, and the ply body portion and the folded portion in the region Has a rubber layer between the thickness of the rubber layer is within 0.58 times the bead core diameter, heavy duty pneumatic radial tire characterized by a wedge rubber is disposed between the folded portion and the chafer.