JPH07232521A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To improve bead durability by making sectional height of a folded part, sectional height of an inside rising part on a steel enforce, sectional height to the tire maximum width and sectional height of a rising part on abrasion rubber in a specified dimensional proportion. CONSTITUTION:When sectional height of an end edge 10A of a folded part 10 on a radial carcass 9 is specified as A, sectional height of an inside rising part 11A on a steel enforce 11 as B, sectional height to the tire maximum width to be a bending point as C and sectional height of a rising part 7 on abrasion rubber 8 as D, C B A D is satisfied. A/C is made to be 40%-50%, and B/C is made to be 50%-60%. Consequently, even when a force from a road surface works on the end edge 10A of the folded part 10 on the carcass 9 as shear force, damage in the neighbourhood of the end edge 10A is certainly prevented and durability is improved.

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 and is used for heavy loads such as trucks and buses.

[0002]

2. Description of the Related Art A pneumatic radial tire of this type is shown in FIG. In FIG. 5, a tire rim 1 includes a rim base portion 2 and a rim flange portion 3, and a bead portion 4 of a pneumatic radial tire is fitted to the tire rim 1. A bead core 5 made of a hexagonal bead wire or the like is embedded in the bead portion 4 over the entire circumferential direction, and a seating portion 6 along the rim base portion 2 and a rising portion 7 along the rim flange portion 3 are integrally formed. An L-shaped abrasion rubber 8 is integrally provided on the outer circumference of the bead portion 4 over the entire circumferential direction.

The radial carcass 9 forms the skeleton of a tire, and is composed of at least one ply in which a steel cord extending in the radial direction is embedded, and its ends are directed from the inner side to the outer side around the bead core 5. Is formed in a folded portion 10 that is folded back and extends in the radially outward direction, and a steel reinforcement 11 having a U-shaped cross section is provided on the outer periphery of the folded portion 10 over the entire circumferential direction.

[0004]

When the pneumatic radial tire according to the prior art shown in FIG. 5 is mounted on a vehicle and used, the force from the road surface is applied to the end edge 10A of the folded portion 10 in the radial direction. To work. Since the rising portion 7 of the abrasion rubber 8 extends radially outwardly of the rim flange portion 3 and is radially outwardly of the end edge 10A of the folded portion 10, the shearing force based on the force from the road surface is relaxed. There were few parts, and peeling, cracks and the like were likely to occur near the edge 10A of the folded portion 10.

The abrasion rubber 8 is compliant with JIS
The A hardness is 65 degrees to 75 degrees, and the rubber thickness E of the rising portion 7 is substantially the same as the rubber thickness F of the side rubber layer 12 that covers the edge 10A of the folded portion 10,
Since the side rubber layer 12 has a low buffering effect, peeling and cracks near the edge 10A are likely to occur, and the side rubber layer 12 is thin, which causes a problem in ozone cracking performance.

Therefore, in the present invention, the bead durability is improved by correlating the cross-sectional heights of the carcass folded-back portion, the inner rising portion of the steel reinforcement, and the rising portion of the abrasion rubber with the cross-sectional height up to the maximum tire width. The first purpose is to do this, and the second purpose is to improve the bead durability and ozone crack performance by making the thickness of the abrasion rubber and the thickness of the side rubber have a correlation.

[0007]

According to the present invention, a seat portion 6 along the rim base portion 2 and a rising portion 7 along the rim flange portion 3 are provided.
An abrasion rubber 8 having a substantially L-shaped cross section is provided in a bead portion 4 in which a bead core 5 is embedded, and an end portion of a radial carcass 9 is folded back from the inner side to the outer side around the bead core 5 and extends radially outward. A pneumatic radial tire T formed on the folded-back portion 10 and provided with a steel reinforcement 11 having a substantially U-shaped cross-section around the folded-back portion 10, which has the following means for achieving the above-mentioned first object. Are taking.

That is, according to the first aspect of the present invention, the sectional height of the folded portion 10 is A, and the sectional height of the inner rising portion 11A of the steel reinforcement 11 is B.
When the sectional height up to the maximum tire width is C and the sectional height of the rising portion 7 in the abrasion rubber 8 is D,
C>B>A> D and A / C is 40%
It is characterized by satisfying the conditions of 50% to 50% and B / C of 50% to 60%.

According to the present invention of claim 1,
The abrasion rubber 8 preferably has a JIS A hardness of 80 to 90 degrees, and the A / C is about 43%.
Is about 46.5%, and the B / C is about 53.
% -Almost 57% and abrasion rubber 8
It is desirable that the JISA hardness of the above is about 85 degrees. Further, in order to achieve the above second object, in the present invention, when the rubber thickness of the rising portion 7 in the abrasion rubber 8 is E and the rubber thickness covering the end edge 10A of the folded portion 10 is F, E It is characterized in that the condition of ≦ 1 / 2F is satisfied.

[0010]

When the pneumatic radial tire T according to the present invention is mounted on a vehicle for traveling, even if the force from the road surface acts on the end edge 10A of the folded portion 10 of the carcass 9 as a shearing force, the end edge 10A It surely prevents damage in the vicinity and improves durability.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. The parts common to those of the above-mentioned prior art are designated by common reference numerals, and the details thereof will be omitted. FIG. 1 shows a left cross section of a pneumatic radial tire T of the present invention according to claims 1 to 3 having a tread ply 13 and an enlarged cross section of an essential part of the pneumatic radial tire T, showing an end edge 10A of a folded portion 10 of a radial carcass 9. The cross-sectional height is indicated by the symbol A, steel reinforcement 1
The cross-sectional height of the inner rising portion 11A in No. 1 is indicated by reference symbol B, the cross-sectional height up to the tire maximum width which is the bending point is indicated by reference symbol C, and the cross-sectional height of the rising portion 7 in the abrasion rubber 8 is indicated by reference symbol D. , And C>B>A> D as shown.

Abrasion rubber 8 has a JIS A hardness of 8
It is set to 0 to 90 degrees to improve rim detachment resistance,
A / C is set to 40% to 50%. Where A / C
40% to 50% is because if it is 40% or less, it becomes too close to the rim flange portion 3 and peeling of the edge 10A is likely to occur due to brake heat or the like. This is because it becomes too close to the edge 11B of the inner rising portion 11A in 11 to cause stress concentration, and the A / C is desirably approximately 43% to approximately 46.5%, as will be clearly shown in the test results described later. To be done.

When A / C is set to 40% to 50%, B /
C is set to 50% to 60%, where B / C is 5
If it is 0% or less, the reinforcing effect by the steel reinforcement 11 is not sufficient, and by setting B> A, the folded portion 1
This is because the movement of the edge 10A at 0 is suppressed to prevent damage, and when B / C is set to 60% or less, it becomes too close to the bending point and stress concentrates on the edge 11B, which causes a damage. , A / C is approximately 43% to approximately 46.5%, B / C is approximately 53% to approximately 57%, as will be apparent from the test results described later.

A first fiber reinforcing layer 14 is laminated on the outside of the folded portion 10 as two inner and outer layers.
Reference numeral 4 extends inward and outward in the radial direction of the edge 10A to prevent damage to the edge 10A. Furthermore, Steel Reinforce 1
In the inner surface of the inner rising portion 11A in FIG.
A second fiber reinforcing layer 15 is superposed along 1A, and the reinforcing layer 15 extends inward and outward in the radial direction of the edge 11B to prevent damage to the edge 11B.

A bead filler rubber 16 having a wedge-shaped cross section is embedded on the bead core 5 over the entire circumferential direction, and a rubber sheet 17 is superposed on the outside of the filler rubber 16 to form side rubbers 12. To prevent delamination. Next, tire size: 1000R2
0, tire internal pressure: 9.0 kgf / cm ² , applied load: 7
A test with a rotating drum having a ton and a speed of 20 km / h was performed on Comparative Examples 1 to 3 and Examples 1 to 4, and the results shown in Table 1 below were obtained.

[0016]

[Table 1]

In Table 1 above, the bead durability of Example 1 according to the present invention is set to 100, and Comparative Examples 1 to 3 and Examples 2 to 4 are shown by indices, and Example 2 is the most bead durable. It can be understood that Examples 3 and 4 are substantially better in bead durability than Comparative Examples 1 to 3. In Comparative Example 1, the cross-sectional height B is large, and B / C
Is around 64%, which is too close to the bending point, and the cause of poor bead durability.

Regarding Comparative Examples 2 and 3, the bead durability was better than that of Comparative Example 2 even though Comparative Example 2 had a higher abrasion rubber hardness (note: indicated by symbol G in Table 1), but A <D From the above, it is understood that the rigidity balance of the bead portion is lost in synergy with the rubber hardness, and the bead durability is inferior to that of any of Examples 1 to 4. 2 to 4
Shows an embodiment of the present invention according to claim 4, and the portions common to FIGS. 1 and 5 are shown by common symbols.

2 to 4, the abrasion rubber 8
The rubber thickness E of the rising portion 7 is set to E ≦ 1 / 2F with respect to the rubber thickness F of the side rubber 12, and the side rubber 12 cushions the movement of the edge 10A of the folded portion 10 to improve the bead durability. At the same time, the ozone crack performance was improved. Tire size: 100
For 0R20, the drum test run was performed by comparing the conventional example shown in FIG. 5 with the example shown in FIG. 2, and it was 180 hours in the conventional example and 237 hours in the example.

Further, regarding the tire size: 11R225, it was 300 hours in the conventional example and 397 hours in the example, and a remarkable difference in bead durability was recognized in each case.

[0021]

As described in detail above, the bead durability can be improved in the present invention according to claims 1 to 3, and the bead durability and ozone crack performance can be improved in the present invention according to claim 4.

[Brief description of drawings]

FIG. 1 is an embodiment of the present invention according to claims 1 to 3, and is an enlarged cross-sectional view of a left half portion and a main portion of a tire.

FIG. 2 is a sectional view showing a first embodiment of the present invention according to claim 4.

FIG. 3 is a sectional view showing a second embodiment of the present invention according to claim 4.

FIG. 4 is a sectional view showing a third embodiment of the present invention according to claim 4.

FIG. 5 is a cross-sectional view of a conventional example.

[Explanation of symbols]

 1 rim 2 rim base part 3 rim flange part 4 bead part 5 bead core 8 abrasion rubber 9 radial carcass 10 folding part 11 steel reinforcement

Claims (4)

[Claims] 1. A seat (6) along the rim base (2).
An abrasion rubber (8) having a substantially L-shaped cross section, which has a rising portion (7) along the rim flange portion (3), is provided in the bead portion (4) in which the bead core (5) is embedded, and the radial carcass (9) is provided. The end portion is formed into a folded-back portion (10) which is folded back from the inner side to the outer side around the bead core (5) and extends radially outward, and a steel reinforcement having a substantially U-shaped cross-section around the folded-back portion (10). A pneumatic radial tire (T) having (11), wherein the cross-sectional height of the folded-back portion (10) is (A), and the inner rising portion (11) of the steel reinforcement (11) is
When the sectional height of (A) is (B), the sectional height up to the maximum tire width is (C), and the sectional height of the rising portion (7) in the abrasion rubber (8) is (D), (C) )>
(B)>(A)> (D), and (A)
/ (C) is 40% to 50% and (B) / (C) is 50
% To 60% of the conditions, The pneumatic radial tire characterized by the above-mentioned. 2. The pneumatic radial tire according to claim 1, wherein the abrasion rubber (8) has a JIS A hardness of 80 to 90 degrees. 3. The (A) / (C) is approximately 43% to approximately 46.5%, and the (B) / (C) is approximately 5.
The pneumatic radial tire according to claim 1, wherein the abrasion rubber (8) has a JISA hardness of about 85 degrees while being 3% to about 57%. 4. A seat (6) along the rim base (2).
An abrasion rubber (8) having a substantially L-shaped cross section having a rising portion (7) along the rim flange portion (3) is provided in the bead portion (4) in which the bead core (5) is embedded, and the radial carcass (9) is provided. Radial tire (T) in which the end portion of the tire is formed into a folded-back portion (10) which is folded back from the inner side to the outer side around the bead core (5) and extends radially outward.
And the rising portion (7) of the abrasion rubber (8)
The rubber thickness of (E), and the edge (1
(E) ≦ 1 when the rubber thickness covering 0A) is (F)
A pneumatic radial tire characterized by satisfying the condition of / 2 (F).