JP2000289408A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of peeling, cracks or slip-off by obliquely cutting off the wound-up end sections of the right and left wound-up sections of a carcass in the inclining direction from the axial inside to the axial outside and from the radial outside to the radial inside. SOLUTION: Lower sections of right and left bead cores 4 of right and left bead sections 2 are wound up from the inside to the outside at both side sections in the width direction of a radial carcass 3. Each wound-up section 5 including a wound-up end section 5 A is covered with an abrasion rubber 7 in the height range of a bead filler 6. The wound-up end section 5A of the carcass 3 is diagonally cut off in the inclining direction from the axial inside to the axial outside and from the radial outside to radial inside. The wound-up height (h) of the carcass 3 is set to about 30.0 mm or below, and the inclination angle of the wound-up end section 5A is set to about 30-60 deg., thereby the occurrence of peeling and cracks can be prevented.

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.

[0002]

2. Description of the Related Art In a pneumatic radial tire, as shown in FIG. 4, both sides in the width direction of a radial carcass 50 forming a tire frame as shown in FIG. One of the techniques for improving the riding comfort while ensuring the steering stability of this kind of pneumatic radial tire is to raise the carcass 50 at both ends in the width direction. A structure for keeping the height low (hereinafter referred to as "LTU structure") is widely known (for example, Japanese Patent Application Laid-Open No. 53-490).
No. 2).

However, in this LTU structure, the carcass 5
In some cases, stress concentration is likely to occur at the upper end portion 52 of the winding 0, and peeling, cracking, and the like are likely to occur with the surrounding rubber layer. Therefore, in order to avoid this, the winding height h of the carcass 50 is increased as much as possible within the allowable range, or the bead filler 53 (provided radially outside the bead core 51 to maintain the winding interval of the carcass 50 is maintained). Of the abrasion rubber 54 (the carcass 5).
Various measures have been sought, such as increasing the thickness of a thicker portion that covers the top end portion 52 of the 0 from the outside with respect to the bead filler 53).

[0004]

Increasing the winding height h of the carcass 50, even if it is kept within an allowable range, leads to a departure from the purpose of the LTU structure, and has a substantially sufficient effect. It was not a suitable measure because it was not possible to obtain Increasing the height H of the bead filler 53 or increasing the thickness of the abrasion rubber 54 not only increases the amount of rubber used and leads to higher costs, but also increases the weight of the tire and increases steering stability. And it could have a negative effect on fuel economy and fuel efficiency.

[0005] On the other hand, when the winding height h of the carcass 50 is further reduced, problems such as peeling and cracking may be less likely to occur. The upper end portion 52 of the carcass 50 is attached to the bead core 5 (during a load such as when inflating or running on a curve).
There is a risk of slipping around around 1, which is not a recommended measure. The present invention has been made in view of the above circumstances, and prevents peeling, cracking, or slip-off at the upper end of a carcass, and also has an adverse effect on steering stability, fuel efficiency, and the like, including an increase in cost. It is an object of the present invention to provide a pneumatic radial tire in which the LTU structure can be meaningfully adopted without affecting the tire.

[0006]

According to the present invention, the following technical measures have been taken in order to achieve the above object. That is, in the pneumatic radial tire according to the present invention, both sides in the width direction of the carcass are rolled up from the inside to the outside of the lower part of the left and right bead cores, and the winding upper part including the winding upper end is within the height range of the bead filler. As a result of repeating various experiments on a structure having a bead portion structure covered with abrasion rubber, the upper end portions of the left and right winding portions in the carcass were directed from the width direction inside to the width direction outside and in the radial direction. It has been found that satisfactory results can be obtained by cutting obliquely in a direction inclined from the outside to the radially inward direction (claim 1).

In this case, it is preferable that the angle of inclination at the upper end of the winding be 30 ° or more and 60 ° or less (claim 2). If the angle is less than 30 °, it is difficult to obtain a sufficient result.
This is because the cutting operation becomes difficult when the angle exceeds °. In addition,
It is assumed that the reason why it is difficult to obtain a sufficient result when the inclination angle is less than 30 ° is that it is difficult to obtain an effect of relieving stress concentration acting on the upper end portion of the winding, particularly strain effect. In order to obtain a sufficient effect of the LTU structure, it is preferable that the winding height of the carcass is 30.0 mm or less (claim 3). Of course, even within this range, if the winding height of the carcass is too low, there is a risk of slipping out of the bead core as described above. It is necessary to appropriately select each case based on empirical rules and the like because it differs depending on the application and the use).

The thickness of the abrasion rubber is 2.0
It is preferable that the thickness be not less than mm and not more than 5.5 mm (claim 4). If the thickness is less than 2.0 mm, the effect of preventing peeling or cracking of the upper end of the carcass cannot be sufficiently improved due to insufficient rigidity of the abrasion rubber. The durability is also insufficient. The thickness of the abrasion rubber is 5.5.
If it exceeds mm, the rubber usage fee as the abrasion rubber increases, leading to an increase in tire weight as well as an increase in cost, which may adversely affect steering stability and fuel efficiency.

It is preferable that the ratio of the height of the bead filler to the cross-sectional height of the tire is not less than 20% and not more than 40%. If it is less than 20%, peeling, cracking or dropout of the carcass hardly occurs even if the upper end of the carcass is not cut obliquely, but the lateral rigidity of the bead filler, that is, the pneumatic radial tire is significantly reduced. Therefore, steering stability is adversely affected, and as a result, adoption becomes difficult. On the other hand, if it exceeds 40%, the rubber usage fee as a bead filler increases, leading to an increase in cost and an increase in tire weight,
This may adversely affect the handling stability and fuel efficiency.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show one embodiment of a pneumatic radial tire 1 according to the present invention. The left and right bead portions 2 of the pneumatic radial tire 1 have left and right bead cores 4 on both sides in the width direction of the radial carcass 3.
Is wound up from the inside to the outside, and the winding upper portion 5 including the winding upper end portion 5A is covered with the abrasion rubber 7 within the height range of the bead filler 6.

The winding upper end portion 5A of the carcass 3 is inclined from the inside in the width direction to the outside in the width direction (from left to right in FIG. 1) and from the outside in the radial direction to the inside in the radial direction (see FIG. 1). 1 (from the top to the bottom). The winding height h of the carcass 3 (the height position of the winding upper end 5)
Is 30.0 mm or less, and the inclination angle θ at the winding upper end 5A is 30 ° or more and 60 ° or less. By making the upper end 5A of the winding oblique as described above, the contact area with the abrasion rubber 7 is increased, which further increases the separation between the upper end 5A of the winding and the bead filler 6, and between the upper end 5 of the winding and the abrasion rubber 7. This is useful for preventing cracks and the like.

The thickness t of the abrasion rubber 7 is 2.0 m
m and 5.5 mm or less. More preferably,
It is 2.0 mm or more and 4.0 mm. Tire section height SH
In contrast, the height ratio of the bead filler 6 is 20%
It is more than 40%. In addition, as shown in FIG. 3, it is more preferable that the edge tape 10 made of a cloth or the like be wound around the upper end portion 5A of the carcass 3, thereby reinforcing the upper end portion 5A of the carcass 3.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Pneumatic radial tire 1 to which the present invention is applied
(Shown in FIGS. 1 and 2) and an exempt pneumatic radial tire (one in which the winding upper end 52 of the carcass 50 is cut normally without being inclined as shown in FIG. 4). An experiment was conducted. The target tire was TL1
It was 75S of 45 / 80R13. Table 1 shows the experimental results.

[0014]

[Table 1]

As is apparent from Table 1, a comparison is made between the pneumatic radial tire 1 to which the present invention is applied and the pneumatic radial tire of Comparative Example 1 (in both cases, it is determined whether the upper end of the carcass is inclined or not). It is understood that the pneumatic radial tire 1 of the present invention is more excellent in durability than the pneumatic radial tire 1 of the present invention except for the difference. In addition, the pneumatic radial tire of Comparative Example 2 has the same durability as the pneumatic radial tire 1 of the present invention, but this is the result of increasing the thickness t of the abrasion rubber. Weight is increasing. Therefore, this comparative example 2
As a result of running tests using a vehicle equipped with a pneumatic radial tire, it has been confirmed that steering stability and fuel efficiency are inferior.

By the way, the present invention is not limited to the above embodiments, and the detailed configuration, shape, material, dimensions and the like can be appropriately changed according to the embodiment.

[0017]

As is apparent from the above description, in the pneumatic radial tire according to the present invention, the upper end portion of the carcass is cut obliquely in a predetermined direction, so that the upper end portion of the carcass is removed from the surrounding rubber layer. Peeling and cracks are prevented. In addition, the LTU structure can be meaningfully adopted without increasing the cost and without adversely affecting the steering stability and fuel efficiency, and without causing the carcass to slip out of the bead core.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a main part of a pneumatic tire according to the present invention.

FIG. 2 is an enlarged view of a top end of a carcass in FIG. 1;

FIG. 3 is a cross-sectional view showing an example in which an edge tape is wound around the upper end of a carcass;

FIG. 4 is a sectional view showing a bead portion structure in a conventional pneumatic tire.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Bead part 3 Carcass 4 Bead core 5 Top end of winding 6 Bead filler 7 Ablation rubber θ Inclination angle of top end of winding h Rolling height of carcass H Height of bead filler t Thickness of abrasion rubber SH Tire cross section height

Claims (5)

[Claims] 1. Both sides of a carcass (3) in the width direction are wound up from the inside of the lower part of the left and right bead cores (4) from the inside to the outside, and the winding upper part (5) including the winding upper end part (5A) is a bead filler (5). In the pneumatic tire having the bead portion (2) structure covered with the abrasion rubber (7) within the height range of (6), the upper end portion (5A) of the left and right winding portions (5) in the carcass (3) is A pneumatic radial tire which is cut obliquely in a direction inclined from the inside in the width direction to the outside in the width direction and from the outside in the radial direction to the inside in the radial direction. 2. The pneumatic radial tire according to claim 1, wherein an inclination angle (θ) at the upper end portion of the winding (5A) is 30 ° or more and 60 ° or less. 3. The pneumatic radial according to claim 1, wherein the winding height (h) of the left and right winding portions (5) in the carcass (3) is 30.0 mm or less. tire. 4. The thickness (t) of the abrasion rubber (7)
The pneumatic radial tire according to any one of claims 1 to 3, wherein the diameter is 2.0 mm or more and 5.5 mm or less. 5. The height ratio (H / SH) occupied by the bead filler (6) to the tire section height (SH) is 20%.
The pneumatic radial tire according to any one of claims 1 to 4, wherein the pneumatic radial tire is not less than 40%.