JPH02310110A - Radial tire - Google Patents

Abstract

PURPOSE:To prevent bead filler from cracking by constituting a down ply by covering the outer surface of bead filler with part of carcass ply, and turning up the remaining part of carcass ply at a portion around bead wire to have its end engaged on the outer surface of down ply. CONSTITUTION:Bead filler 12 is let extended from the upper end of bead wire 10 toward the outside in the radial direction of a tire, and the upper end is positioned higher than the height of the maximum width W of the tire. Carcass ply 16 on the outside covers the outer surface of the bead filler 12 as down ply, and its lower end 18 is positioned at the same height as the lower end of the bead wire 10. On the other hand, carcass ply 14 on the inside is let down along the inner surface of the bead filler 12, then turned up outward from the inside at around the bead wire 10, and the turned-up portion is engaged on the outer surface of the outside ply 16. Furthermore, chafer 22 is arranged in a manner to cover the outer surface of the turned-up portion of the inside ply 14 and part of the outer surface of the outside ply 16.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a radial tire having a plurality of carcass plies and a bead portion having a bead wire and a bead filler radially outward of the bead wire. ``Improve the durability of parts'' - related to things that have been stirred.

[Prior Art] FIG. 2 is a cross-sectional view of a beat portion of a conventional radial tire.

A bead wire 10 is disposed at the bead 1 of this tire, and a bead filler 12 having a wedge-shaped cross section extends radially outward from the upper end of the wire. As the bead filler 12, rubber whose rigidity is increased by adding carbon black or phenol resin is used. The upper end of this bead filler 12 reaches a height 17 higher than the maximum width W of the tire. The carcass plies are 2 piece-C.

A first braai 14 is disposed on the inner liner-1-1, and a second braai 16 is disposed on the outside of the first braai I4. As these carcass plies 14 and 16, for example, a carcass cord made of S.R.Ron fiber and covered with rubber is used. Both of the double-sided cusp plies 14 and 16 descend along the inner surface of the bead filler 12 and then are wound up around the bead wire 10 from the inside to the outside to form a turn-up bly. At this time, the rolled up portion of the second braai 16 is locked to the outer surface of the bead filler 12, and its braai end J8 is located near the upper end of the bead filler 12. 1st ply 14
The rolled portion of the second braai 16 contacts the outer surface of the rolled portion of the second braai 16 and terminates on the bead filler 12 at a position 20 higher than its end 18 . Further, the outer side of the conical portion of these carcass plies 14.1.6 is completely covered with a chafer 22. That is, the lower end 24 of this chafer 22 is approximately the same height as the lower end of the bead wire IO, and is higher than the upper end 2G or the end 2o of the first ply 14. For example, a nylon cord topped with rubber is used as the chafer 22.

FIG. 3 is a sectional view of a bead portion of another conventional radial tire.

This tire also has a large bead filler 12 similar to that in FIG. The first ply 14 includes a bead filler 1
After descending along the inner surface of the bead wire 10, it is wound from the inside to the outside around the bead wire 10 to form a turn-up braai. The rolled up portion of this first ply 14 is
It is secured to the outer surface of the beet filler 12 and terminates at a relatively high position 20. On the other hand, the second bly 16 serves as a down ply with the remaining portion of the outer surface of the bead filler 12 and the first bly.
The outer surface of the rolled up portion of the ply 14 is completely covered.

In other words, the end portion 18 of the second braai 16 is approximately at the same height as the lower end of the beehive 10.Furthermore, a chafer 22 is disposed outside the second braai 16.

The chafer 22 has a lower end 24 approximately at the same height as the end 18 of the second braai 16, and an upper end 26 approximately at the height of the maximum width W of the tire.

In all of the conventional radial tires described above, not only is the bead filler 12 having relatively high hardness reaching above the height of the tire maximum width W, but also the bead filler 12 is large and has carcass plies on both sides of the bead filler 2. 1
4.1 The rigidity of the beat portion is high because it is covered with i. Therefore, it is known that even though it is a radial tire, it can prevent wandering on rutted roads and provide high running stability. Note that the chafer 22 is inserted for the purpose of further increasing the rigidity of the bead portion and protecting this portion from external damage.

[Problems to be Solved by the Invention] Now, at the braai ends 1.8 and 20, the cut ends of the carcass cord are exposed. Therefore, separation between the topping rubber and the carcass cord is likely to occur at the braai end 18.20 due to concentrated stress during tire running.

However, in the conventional radial tire shown in FIG. 2, both ply ends 18 and 20, and in the conventional radial tire shown in FIG. 3, the end 2° of the first ply 14 contacts the outer surface of the bead filler 12. As a result, the relatively brittle bead filler 12 may be damaged by the separator at the cut end of the cord, causing the bead filler 12 to crack. If cracks occur in the bead filler 12, the required bead rigidity cannot be obtained and the tire cannot run.

The present invention has been made in view of the above points, and provides a radial tire having a plurality of carcass plies and a bead portion having a bead wire and a beat filler radially outward of the bead wire. The purpose of this method is to prevent cracking of the bead filler and improve the durability of the bead portion by reducing the amount of the bead filler.

[Means for Solving the Problems] In order to achieve the above object, the radial tire according to the present invention includes a down ply in which a part of the carcass ply that reaches the bead wire covers the outer surface of the bead filler, and The remaining carcass ply is wound around the bead wire from the inside to the outside, and the ends of this braai are locked to the outer surface of the down ply.

[Function] The down ply does not terminate on the outer surface of the bead filler, but reaches the bead wire. The ends of the turn-up ply lie on the outer surface of this down ply. In other words, neither ply end comes into direct contact with the bead filler. Therefore, even if separation occurs at the cut end of the carcass cord, the bead filler will not be damaged by this separation.

Embodiment FIG. 1 is a sectional view of a bead portion of a radial tire according to an embodiment of the present invention.

Similar to the tires shown in FIGS. 2 and 3, this tire also has a bead wire 10 disposed at the bead portion, and a bead filler 12 having a wedge-shaped cross section extends outward in the radial direction of the tire from the upper end of this wire.

Furthermore, the upper end of the bead filler 12 reaches above the height of the tire maximum width W. 2 carcass plies 1.
4,] The outer second bly 16 of 6 completely covers the outer surface of the bead filler 12 as a down ply,
The bead wire 10 is reached. In other words, this second braai 1
The end 18 of 6 is substantially flush with the lower end of the bead wire 10. On the other hand, the first braai 14 includes the bead filler 1
After descending along the inner surface of the bead wire 10, it is wound up from the inside to the outside around the bead wire 10 to form an evening up braai h'. The winding part of this first braai 14 is
A relatively high position 2 connected to the outer surface of the second braai 16
Terminates with 0. Furthermore, a chafer 22 is disposed so as to cover the outer surface of the rolled-up portion of the first braai 14 and a part of the outer surface of the second braai 16. In other words, this Chafer-22
is approximately the same height as the lower end 24 or the end 18 of the second braai 1G, and the upper end 26 is approximately the same height as the maximum width W of the tire.

The radial tire according to the embodiment of the present invention described above not only has a large bead filler 12, but also carcass plies 14 on both sides of the bead filler 12. ．． 1
Since it is covered with G, the rigidity of the bead part is high. Therefore, since it is a radial tire, it is possible to prevent the phenomenon of wandering on rutted roads, and high running stability can be obtained. Moreover, since neither of the ply ends 1.8 and 20 comes into direct contact with the bead filler 12, even if separation occurs at the cut end of the carcass cord, the bead filler 12 will not be damaged by this. do not have.

In addition, the insulation rubber is carcass ply 1.4
, 1.6 or increasing the thickness of the topping rubber of the carcass plies 14 and 1.6 are effective in suppressing the occurrence of separation itself.

In order to verify the above effects, we made the following four types of radial tires and conducted drum tests. That is, the tires of Examples 1 and 2 have the bead structure shown in FIG.

However, the topping rubber thickness of the carcass ply in Example 2 is approximately twice that of Example 1. The tires of Comparative Examples 1 and 2 have the tire structure shown in FIGS. 2 and 3, respectively.

The tire sizes are 6.5OR161, 0PR, and everything else is the same except for the bead structure. The results of the drum test are shown in Table 1. Furthermore, as a result of actual vehicle feeling tests on rutted roads, both tires have achieved high running stability.

Table 1 In addition, when using three or more carcass plies,
After covering the outside of the beet filler 12 with a part of the carcass ply to form a down ply, the remaining carcass ply is wound up around the bead wire 10 and the end of this ply is locked to the outside of the down ply. . When a large bead filler 12 is used as in this embodiment, there is an effect of preventing wandering as described above, but the present invention is applicable not only to radial tires having large bead fillers.

[Effects of the Invention] As explained above, in the radial tire according to the present invention, a part of the carcass ply reaching the bead wire covers the outer surface of the bead filler to form a down ply, and then the remaining carcass ply is attached to the bead wire. The end of this braai is locked to the outer surface of the down ply, so that neither end of the ply comes into direct contact with the beat filler, and the cut end of the carcass cord If separation occurs, this will not damage the bead filler. That is, according to the present invention, cracking of the bead filler can be prevented and the durability of the bead portion can be improved.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the bead portion of a radial tire according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of the bead portion of a conventional radial tire, and FIG. 3 is a cross-sectional view of the bead portion of another conventional radial tire. FIG. Explanation of No. 71 10. Bead wire, 12. Beat filler, 1
4゜16...Carcass ply, 1.8.20...Ply end, 22 Chafer-1W Tire maximum width. Patent applicant Toyo Rubber Co., Ltd. Figure 1 Figure 2-71 = Figure 3

Claims (1)

[Claims] 1. In a radial tire that has a plurality of carcass plies and a bead portion that has a bead wire and a bead filler radially outward of the bead wire, a part of the carcass ply that reaches the bead wire covers the outer surface of the bead filler to form a down ply. The radial tire is characterized in that the remaining carcass ply is then wound around the bead wire from the inside to the outside, and the end of this ply is locked to the outer surface of the down ply.