JPH01285410A - Heavy load pneumatic radial tire - Google Patents

Abstract

PURPOSE:To improve the durability of a bead portion by disposing a turn-up ply in a designated region from an rim flange to the tread side and a turn-up portion substantially parallel at a designated space therebetween when a tire is installed on a normal rim and normal internal pressure is charged therein. CONSTITUTION:In the radial section of a tire which is installed on a normal rim and is charged with normal internal pressure, a turn-up ply of a carcass 1 and a turn-up portion 2 in a region clamped by a tangent (m) drawn from a rim flange 5 parallel to the rotating shaft of the tire and a line (n) drawn parallel at a position distant from the line (m) by 2/3 times the height of the rim flange are disposed in such a manner as to be substantially d1$1 d2, and the space between the ply and the turn-up portion 2 is set within 0.60 times as long as the diameter l of a bead core 4. By this arrangement, separation between rubber of the bead core portion and a cord can be prevented so as to improve durability.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a pneumatic radial tire for heavy loads such as trucks or buses, and particularly describes a technique for improving the durability of the bead portion.

(Prior Art) Since it is essential for heavy-duty tires to withstand heavy loads, the bead portion thereof has a turn-up ply structure in which the ply of the carcass is wound around the bead core from the inside of the tire to the outside.

This type of tire is used under heavy loads, so if a chafer is provided outside the folded part of the ply at the bead or as a reinforcing material, the rubber and cord will peel off on the outside of the chafer, making it unusable. It often becomes.

Conventionally, methods for improving the adhesion between the rubber and the cord or improving the quality of the rubber have been known to address delamination between the rubber and the cord, but methods for improving the structure of the tire are unknown.

(Problems to be Solved by the Invention) Therefore, the present invention aims to prevent the rubber from separating from the cord at the bead portion by improving the structure of the bead portion, thereby improving the durability of the bead portion.

(Means for Solving the Problems) This invention consists of a ply in which cords are arranged parallel to each other in a direction perpendicular to the equatorial plane of the tire, and at least one ply is arranged around a pair of bead cores from the inside of the tire. A pneumatic radial tire with a toroidal carcass, which is a turn-up ply with a folded part wound outward, is mounted on a regular rim and filled with the regular internal pressure. Parallel tangent line of the rim flange and 2/3 of the rim flange height from this tangent line to the tire tread side.
The ply of the turn-up ply and the folded portion in the area sandwiched between the parallel lines separated by the fold are substantially parallel to each other, and
A pneumatic radial tire for heavy loads, characterized in that the interval between the ply and the folded part is within 0.60 times the bead core diameter, and the cords are arranged in parallel to each other in a direction perpendicular to the equatorial plane of the tire. a toroidal carcass consisting of plies, at least one ply of which is a turn-up ply having a folded part wound from the inside to the outside of the tire around a pair of bead cores; a chafer disposed on the outside of the tire in the folded part; When a pneumatic radial tire is installed on a regular rim and filled with the regular internal pressure, the radial cross section of the tire has a tangent to the rim flange that is parallel to the axis of rotation of the tire, and a rim flange height that extends from this tangent to the tire tread side. 2/3 of the way
The ply of the turn-up ply and the folded portion in the area sandwiched between the parallel lines separated by the fold are substantially parallel to each other, and
This is a pneumatic radial tire for heavy loads, characterized in that the interval between the ply and the folded part is within 0.60 times the bead core diameter, and a wedge rubber is disposed between the folded part and the chafer.

Now, FIG. 1 illustrates the structure of a bead portion of a heavy-duty pneumatic radial tire according to the present invention.

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

In the carcass 1, the ply and the folded portion 2 are substantially in the region sandwiched between a tangent line m of the rim flange 5 parallel to the tire rotation axis and a parallel line n separated by 2/3 times the rim flange height H. upper parallel (dtζd2) and the interval is within 0.60 times the diameter β of the bead core 4 (di ≦0.60
A).

Further, FIGS. 2(a) to 2(C) show other bead portion structures according to the present invention. In both examples, the distance between the ply and the folded portion in the region sandwiched between the tangent line m and its parallel line n is d! =id.

Of course, it is arranged so that di <0.60A.

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

Here, the wedge rubber 6 is a tire that extends one layer three times the height of the rim flange to the tire tread side from a straight line parallel to the tire rotation axis passing through the maximum width position of the bead core and a tangent line of the rim flange parallel to the tire rotation axis. It is desirable to arrange it in a range sandwiched between two straight lines parallel to the axis of rotation.

(Function) The destructive phenomenon that leads to the separation of the rubber and cord at the bead is caused by shear strain within the tire's radial cross section when the tire is transferred. As a result of research, we found that this occurs when

On the other hand, in the tire according to the present invention, the ply and the folded part in the bead part are arranged substantially parallel, and the distance d1 between the folded part and the ply is set to within 0.60 times the bead core diameter. The deformation during transfer can be changed from shear deformation to bending deformation. Therefore, shear strain occurring at the rim-side interface of the folded portion of the ply is reduced, and peeling between the rubber and the cord can be suppressed.

Another reason for arranging the ply in the bead portion and the folded portion substantially in parallel is to make the shear deformation uniform in the failure area and to prevent the shear deformation from concentrating in one part.

For manufacturing convenience, a chafer is placed on the outside of the folded part of the ply in order to avoid the disadvantage of so-called rubber flow in the pot during vulcanization in the tire manufacturing process.
Furthermore, it is effective to provide a wedge rubber between the chafer and the folded portion. i.e. chafer
The flow of rubber between the folded part and the folded part is sealed, so that the folded part and the ply can be arranged substantially in parallel, and so-called gouging of the bead part can be easily realized.

(Example) Heavy-duty tires of size 10.0OR20 with radial structure carcass using steel cord ply were manufactured with bead parts having the structure shown in Figs. 1 to 3. The distance traveled until the ply folds or the chafer peels off from the rubber is measured during running, and the results are listed in the attached table as an index when the conventional tire with the structure shown in Figure 3 is taken as 100. show. Note that the distances d, d2 between the folded portion and the ply and the bead core diameter l in each tire are also listed in the table below.

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

[Brief explanation of the drawing]

1 and 2 (a) to (C) are cross-sectional views showing a bead structure according to the present invention, and FIG. 3 is a cross-sectional view of a conventional bead portion. l... Carcass 2... Turned part 3...
Chafer 4... Bead core 5... Rim flange 6... Wedgecom patent applicant Bridgestone Corporation

Claims (1)

[Claims] 1. Consisting of a ply in which cords are arranged parallel to each other in a direction perpendicular to the equatorial plane of the tire, at least one
The ply is a pneumatic radial tire with a toroid-shaped carcass, which is a turn-up ply with a folded part that is wound from the inside to the outside of the tire around a pair of bead cores, and is mounted on a regular rim and filled with the regular internal pressure. In the radial cross section of the tire in this condition, there is a tangent line to the rim flange that is parallel to the axis of rotation of the tire, and a line extending from this tangent line to the tire tread side by 2/3 of the rim flange height.
The ply of the turn-up ply and the folded part in the area sandwiched between the parallel lines separated by the same width are arranged substantially parallel to each other, and the distance between the ply and the folded part is set within 0.60 times the bead core diameter. A pneumatic radial tire for heavy loads. 2. Consisting of a ply in which cords are arranged parallel to each other in a direction perpendicular to the equatorial plane of the tire, at least one
A pneumatic radial tire with a toroidal carcass, which is a turn-up ply with a turn-up ply that is wound from the inside to the outside of the tire around a pair of bead cores, and a chafer placed on the outside of the turn-up part. Then, in the radial cross section of the tire when it is mounted on a regular rim and filled with the regular internal pressure, there is a tangent line of the rim flange that is parallel to the axis of rotation of the tire, and a distance of 2/3 of the rim flange height from this tangent line to the tire tread side.
The ply of the turn-up ply and the folded part in the region sandwiched by the parallel lines separated by the double are arranged substantially parallel, and the interval between the ply and the folded part is set to 0.60% of the bead core diameter.
A pneumatic radial tire for heavy loads, characterized by having a wedge rubber between the folded part and the chafer.