JPH0820208A - Large pneumatic radial tire - Google Patents

Abstract

PURPOSE:To provide a tire which does not cause rim slide easily, that is, a tire in which rubber on a surface in contact with rim of a bead base section of the tire does not wear easily and consequently, a failure due to air leakage does not occur easily. CONSTITUTION:It is a large pneumatic radial tire in which a bead core has a shape of downward projection on its bead base side, its maximum size of projection (N) is 30-80% of vertical distance (M) from a bottom surface (D) of normal hexagon bead core to the maximum width position (P) on the inner side of tire of the bead core, and the maximum width position (Q) on rim-flange side of the bead core is continuous with the projection by smooth projected curve.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a large pneumatic radial
The present invention relates to bead cores for tires, and more particularly to large pneumatic radial tires used in heavy trucks, construction vehicles or industrial vehicles.

[0002]

2. Description of the Related Art Conventionally, a typical bead core used in a large pneumatic radial tire has a cross-sectional shape that is symmetrical in the vertical and horizontal directions as shown in FIG. It was a regular hexagonal bead core (4) without a taper. Regular hexagonal bead cores include, but are not limited to, regular hexagonal shapes. In the present specification, a regular hexagonal bead core is a hexagonal cross-sectional shape that is vertically symmetrical with respect to a horizontal plane including the center point of the bead core and symmetrical with respect to a vertical plane including the center point in the left-right direction. Means bead core.

A large pneumatic radial tire (1) having the conventional regular hexagonal bead core (4) as described above.
Then, when the torque transmitted from the vehicle to the tire becomes larger than a certain amount, slippage (rim slip) occurs between the bead base portion (B) of the tire (1) and the bead seat portion (S) of the rim (3). Occurs, and the rubber on the surface where the bead base portion (B) of the tire (1) contacts the bead seat portion (S) of the rim (3) is worn. If this wear progresses, it will eventually lead to an air leakage failure. The pressure distribution under the bead core of the tire (1) having the conventional regular hexagonal bead core (4) has a high pressure on the bead heel part (H) side and a high pressure on the bead toe part (T) side. Since the pressure is low, the rubber (h) on the bead heel part (H) side, which has a higher pressure than the rubber (t) on the bead toe part (T) side, which has a lower pressure
Will tend to wear more. Due to variations in tire manufacturing, the thickness of the rubber under the bead core may
When a tire that is thinner on the heel portion (H) side and thicker on the bead toe portion (T) side is manufactured, this pressure difference increases, and the above-described wear tendency is promoted. Also, when the tire is filled with internal pressure and subjected to repeated deformation under load and rotation, rotation of the bead core occurs, and the thickness of the rubber under the bead core becomes thin on the bead heel (H) side, Since the bead / toe (T) side becomes thicker, the above wear tendency is promoted.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide a tire in which rim slippage is unlikely to occur. In other words, it is an object of the present invention to provide a tire in which the rubber contacting the rim of the bead base portion of the tire is less likely to be worn, and thus the occurrence of air leakage failure is reduced.

[0005]

In order to achieve the above object, a tire of the present invention is a pneumatic tire having a pair of left and right bead cores and a radial carcass fixed to the bead cores and extending between the bead cores. In the filled tire, the bead core has a downward convex shape on the bead base side, and the maximum convex portion size (N) is from the bottom surface (D) of the regular hexagonal bead core to the bead core. It is 30 to 80% of the vertical distance (M) to the tire inner maximum width position (P), and is connected to the convex portion with a smooth convex curve from the rim flange side maximum width position (Q) of the bead core. It is a large pneumatic radial tire characterized by its shape.

[0006]

[Function] Compared with the pressure distribution under the bead core of the conventional regular hexagonal bead core in which the pressure peak exists on the bead heel side (rim flange side), in the tire according to the present invention, the bead core Has a downwardly convex shape on the bead base side, the pressure on the bead toe portion side rises, and the pressure is dispersed as a whole. Also,
In the tire according to the present invention, the pressure is dispersed because the bead heel side of the bead core has a smooth convex curve shape. As a result, slippage (rim slippage) between the bead base portion of the tire and the bead seat portion of the rim is prevented or suppressed.

Further, compared to the conventional regular hexagonal bead core, even if the bead core rotates, the bead of the rim
The difference in the distance from the seat to the bead core of the tire will be smaller and therefore the pressure difference will also be smaller.

The bead core of the tire according to the present invention has a downward convex shape on the bead base side, and the maximum convex portion size (N) is from the bottom surface (D) of the regular hexagonal bead core to the bead core. 30% to 80% of the vertical distance (M) from the core to the tire inner maximum width position (P), but if it is 30% or less, the above pressure dispersion effect cannot be obtained, and if it is 80% or more. On the contrary, a pressure peak occurs on the bead toe side.

[0009]

EXAMPLES Examples according to the present invention will be described with reference to the drawings. The tires (1) of Examples 1 to 4 according to the present invention shown in FIG. 1 are construction vehicle tires and have a tire size of 26.5R25. is there. The tire (1) of Example 1 according to the present invention comprises a radial core made of a pair of left and right bead cores (2) and a steel cord fixed to the bead cores (2) and extending between the bead cores (2).
It has a carcass (not shown). The bead core (2) has a downward convex shape on the bead base (B) side as shown in the drawing, and the maximum convex portion size (N).
Is 3 mm. This is 30% of the vertical distance (M = 10 mm) from the bottom surface (D) of the regular hexagonal bead core to the tire inner maximum width position (P) of the bead core (2). From the maximum width position (Q) on the flange (F) side of the rim (3) of the bead core (2) to a straight line passing through the apex of the convex portion on the side of the bead base (B) with an arc having a radius of R = 10 mm. It is in a row. Width (L) of the bead core (2)
Is 32 mm.

The tire (1) of Example 2 according to the present invention is
The maximum convex portion size (N) of the bead core (2) is 4
The same as Example 1 except that the radius (R) of the circular arc from the flange (F) side maximum width position (Q) is 12 mm.

The tire (1) of Example 3 according to the present invention is
The maximum protrusion size (N) of the bead core (2) is 6
The same as Example 1 except that the radius (R) of the circular arc from the flange (F) side maximum width position (Q) is 12 mm.

The tire (1) of Example 4 according to the present invention is
The maximum convex portion size (N) of the bead core (2) is 7
The same as Example 1 except that it is mm.

For comparison with the above-mentioned embodiment according to the present invention, a conventional tire (1) having the same tire size shown in FIG. 5 was evaluated under the same conditions. Conventional tire (1)
Is the same as Example 1 except that the bead core is a regular hexagonal bead core (4).

Embodiments of the bead core (2) according to the present invention other than the above embodiments are shown in FIGS.

The above Examples 1 to 4 according to the present invention and the conventional example were evaluated under the same conditions. As an evaluation method, a static load tester was used to measure the rim slip resistance generated at the bead portion when the tire was set in a braking state and the tread plate was moved.

The evaluation results are shown in index form with the result of the pneumatic tire of the conventional example as 100, and the larger the number, the better the performance. Table 1 shows a summary of the evaluation results.

[0017]

[Table 1]

From the results shown in Table 1, the pneumatic tires for construction vehicles of Examples 1 to 4 according to the present invention have far better rim slip resistance than the pneumatic tires for construction vehicles of the above-mentioned conventional examples. I found out that

[0019]

According to the present invention, since the pneumatic tire is provided with the bead core having the above-described shape, the rim slip resistance is excellent, and the rubber on the surface that comes into contact with the rim of the bead base portion of the tire is It has become possible to provide a tire that is less likely to wear and therefore has less air leak failure.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a bead portion of a tire according to an embodiment of the present invention.

FIG. 2 is a sectional view of a bead portion showing another embodiment according to the present invention.

FIG. 3 is a sectional view of a bead portion showing another embodiment according to the present invention.

FIG. 4 is a bead portion sectional view showing another embodiment according to the present invention.

FIG. 5 is a cross-sectional view showing a bead portion of a conventional tire.

[Explanation of symbols]

 1 tire 2 bead core 3 rim 4 regular hexagonal bead core B bead base part D regular hexagonal bead core bottom face F rim flange H bead heel portion L bead core width M bottom face (D) maximum width Vertical distance to the position N Maximum convex size P Maximum width inside the tire of the bead core Q Maximum width at the flange side of the bead core S Rim bead seat T Bead toe h Rubber at the bead heel Rubber on the bead and toe side

Claims (1)

[Claims] 1. A pair of left and right bead cores and the bead cores.
In a pneumatic tire having a radial carcass fixed to the core and extending between the bead cores,
The bead core has a downward convex shape on the bead base side, and the maximum convex portion size (N) is from the bottom surface (D) of the regular hexagonal bead core to the tire inner maximum width of the bead core. It is 30 to 80% of the vertical distance (M) to the position (P), and the shape is continuous from the flange-side maximum width position (Q) of the bead core to the convex portion with a smooth convex curve. Large pneumatic radial tires.