JP2001071718A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively suppress rupture and damage of a carcass code without preventing reduction in a cost and productivity even in the case where a bead filler is eliminated. SOLUTION: A bean apex rubber 9 is equipped with a main part 9A extending from an outward surface S1 in the radial direction of a bead core 5 to the radial outside and a blade part 9B which is connected to the main part 9A, brought into contact with an inward surface S3 in the axial direction of the bead core 5, and extends in a radial inward. The radial length A of the blade part 9B from the outward surface S1 of the bead core 5 is set to 0.3-1.0 times the cross sectional height H of the bead core 5. The thickness B of the blade part 9B from the inward surface S3 is set to 0.3-1.5 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire capable of alleviating rubbing between an edge portion of a bead core and a carcass cord when a bead filler is removed and maintaining bead durability.

[0002]

2. Description of the Related Art A pneumatic tire usually has a structure shown in FIG. 4 (A) in order to reinforce the bead portion and secure the lateral rigidity of the tire.
As shown in FIG. 1, a bead apex rubber b made of hard rubber extending radially outward from a bead core a is arranged.

[0003] The bead apex rubber b is generally wrapped in a U-shape with the bead core a by a cord reinforcing layer called so-called bead filler c using a nylon cord textile cloth. It has been proposed to eliminate the bead filler c for the purpose of improving productivity.

On the other hand, the bead core a often has a tape bead structure having a rectangular cross section formed by winding a plurality of layers of tape-like strands in which four to six bead wires are horizontally aligned.

[0005]

However, when the bead filler c is eliminated from the bead core a having such a bead structure, as shown in FIG. 4B, the bead deformation under load (outward in the tire axial direction) occurs. When the bead core a falls, the carcass cord d is repeatedly bent at the inner edge portion P in the tire axial direction and the outer edge portion in the radial direction. As a result, in combination with the direct rubbing between the carcass cord d and the bead wire, there is a problem that the bead durability is reduced, such as causing breakage of the carcass cord d at the edge portion P.

Accordingly, the present invention is based on the fact that a bead apex rubber is provided with a wing portion of a predetermined size extending inward in the radial direction in contact with the tire core inward surface in the tire axial direction. The pneumatic tire can reduce the concentration of strain at the edge portion P of the carcass cord and the direct rubbing with the bead wire, and can suppress breakage damage of the carcass cord without reducing cost and productivity. It is intended to be provided.

[0007]

In order to achieve the above object, a carcass folded back around a bead core buried in a bead portion from a tread portion to a sidewall portion through a sidewall portion, and A pneumatic tire comprising a bead apex rubber extending radially outward from the bead core, wherein the bead core is formed using a bead wire and has a rectangular cross-section having a radially inward surface substantially in the tire axial direction. In addition, the bead apex rubber extends radially inward from a radially outward surface of the bead core and a main portion extending radially outward from the radially outward surface of the bead core and in contact with the tire axially inward surface of the bead core. And a radial length A of the wing from the outward surface of the bead core is defined by a cross-sectional height H of the bead core. .3～1.0 times and is characterized in that the thickness B from the inward surface of the blade portion was 0.3 to 1.5 mm.

In the invention of claim 2, the bead apex rubber has a durometer A hardness of 60 to 95 degrees.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, a pneumatic tire 1 includes a tread portion 2, sidewall portions 3 extending inward in the tire radial direction from both ends thereof, and a bead portion located at the tire radially inner end of each sidewall portion 3. 4
And Further, the pneumatic tire 1 includes a toroidal carcass 6 bridged between the beads 4, and a bead apex rubber 9 extending radially outward from a bead core 5 embedded in the beads 4. Provided.

The carcass 6 includes a ply body 10A extending from the tread portion 2 to the bead core 5 through the sidewall portion 3 and a ply body portion 10A. And an inner carcass ply 10 having a ply turn-up portion 10B that is turned out. In this example, the carcass ply 1
0, and a carcass 6 having a so-called 1-1 structure composed of a carcass ply 20 disposed outside the carcass ply 20. The outer carcass ply 20 extends from the tread portion 2 to the outside of the ply folded portion 10B. Rolled down through the sides.

In the present embodiment, each of the carcass plies 10, 20 has a carcass cord arranged at an angle of 70 to 90 ° with respect to the tire equator C. As the carcass cord, in addition to a steel cord, for example, nylon or polyester Organic fiber cords such as aromatic polyamides are preferably used.

A belt layer 7 is wound around the outside of the carcass 6 and inside the tread portion 2 in the circumferential direction to reinforce the tread portion 2 with a hoop effect and increase the tread rigidity. This belt layer 7 is composed of two or more steel cords, aromatic polyamides or other high-elasticity belt cords arranged at an angle of 10 to 35 degrees with respect to the tire equator C,
In this example, the belt ply is composed of two belt plies 7i and 7o, and the belt cords are overlapped with the inclination directions of the cords being different from each other so as to intersect between the plies.

The bead apex rubber has a main portion 9A which extends between the ply body portion 10A and the ply folded portion 10B and extends radially outward from the radially outward surface S1 of the bead core. 9 are provided. In this example, a structure in which a cord reinforcing layer such as a so-called bead filler c that wraps and integrates the bead apex rubber 9 and the bead core 5 in a U-shape is removed from the bead portion 4. Therefore, the carcass 6 is folded back without interposing a cord reinforcing layer between the carcass 6 and the bead core 5.

Next, the bead core 5 forms a ring-shaped body having a rectangular cross section formed by winding a bead wire 11 (shown in FIG. 2). This example illustrates a tape bead structure in which a ribbon-like strand in which a plurality of bead wires 11 are horizontally aligned is spirally wound from the inside to the outside in the radial direction. In this manner, the bead core 5 has a rectangular cross section, and the radially inward surface S2 is disposed substantially in the tire axial direction. Note that, as the bead wire 11, for example, a wire material such as an aromatic polyamide fiber may be used in addition to steel such as a steel wire.

If the bead core 5 has a rectangular cross section, one bead wire 11 that has been rubberized in advance is used.
Can be used in a single-wind structure in which helical winding is continuously performed.

In the present application, as shown in FIG. 2, the bead apex rubber 9 is connected to the main portion 9A and comes in contact with the tire axially inward surface S3 of the bead core 5 and extends radially inward. 9B.

The main portion 9A has a triangular cross-section extending from the radially outward surface S1 of the bead core 5 toward the radially outward side. The height H1 of the radially outer end of the main portion 9A from the bead base line L is not particularly limited, but is approximately the same as the conventional height, that is, from the outer end height of the rim flange to the tire maximum width position height. Ranges are commonly employed.

The wing portion 9B extends radially inward beyond the radially outward surface S1 and forms a covering portion overlapping the radially inward surface S2 of the bead core 5. Thereby, the edge portion P of the bead core 5 inward in the tire axial direction and radially outward can be covered. As a result, the bending and contact pressure of the carcass cord at the edge portion P can be reduced, the concentration of strain can be reduced, and the direct contact between the carcass cord and the bead wire can be prevented, and the breakage of the carcass cord can be effectively suppressed. And bead durability can be improved.

For this purpose, the radial length A of the wing portion 9B from the radially outward surface S1 is determined by the bead core 5B.
And the thickness B of the wing portion 9B from the tire axial direction inward surface S3 is 0.3 to 1.0 times the sectional height H of the wing portion 9B.
It needs to be 1.5 mm.

When the length A is less than 0.3 × H and when the thickness B is less than 0.3 mm, the protection to the edge portion P becomes insufficient, and the effect of suppressing the breakage of the carcass cord is reduced. It can no longer be used effectively. On the other hand, when the length A exceeds 1.0 × H, the compression under the core is reduced, and the fitting property with the rim is impaired. On the other hand, if the thickness B exceeds 1.5 mm, the rubber volume increases unnecessarily, and the heat generated by the rubber adversely affects the bead durability.

Here, the "cross-sectional height H" means a distance between the radially inward surface S2 and the radially outward surface S1 of the bead core 5.

The "thickness B" means the thickness of the edge portion P from the inward surface S3 of the wing portion 9B in the tire axial direction. That is, the wing 9B is, as in this example,
It is preferable from the viewpoint of productivity and the like to form a substantially constant thickness over the entire length, but the thickness can be partially changed. For example, as schematically shown in FIGS. 3A to 3C, a thickness-reduced portion 13 having a gradually decreasing thickness is provided inside a radially inward portion of a constant-thickness portion 12 having a substantially constant thickness. The one having the wing portion 9B formed only by the reduced thickness portion 13 without having the portion 12 or the one having the reduced thickness portion 13 provided radially below the thickened portion 14 whose thickness is gradually increased can also be suitably used.

When the wings 9B are formed only by the equal thickness portions 12, for example, as schematically shown in FIG. 3D, the inner surface of the main portion 9A having a width W substantially equal to that of the bead core 5 is formed.
The rubber piece 15 is attached to the bead core 5 so that the rubber piece 15 adheres to the bead core 5.
A can also form the wing 9B.

In any case, the main portion 9A and the wing portion 9B are made of the same rubber and have a durometer A hardness of:
In order to obtain the required bead rigidity, it is preferable that the angle be in the range of 60 to 95 degrees as in the case of the conventional bead apex rubber. The durometer A hardness is JIS-K6253.
Is a durometer type A based on

The wings 9B are also useful for improving the bonding strength with the bead core 5, and the bead apex rubber 9 may be peeled off from the bead core 5 at the time of, for example, storage or transportation prior to introduction into the tire production line. Failure can be prevented.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A tire having the structure shown in FIG.
A 16 12PR tire was prototyped based on the specifications in Table 1, and the bead durability of each test tire was tested. The results are shown in Table 1.

(1) Bead durability: A sample tire was run on a drum at a speed of 20 km / h using a drum tester under conditions of a rim (5.50), an internal pressure (600 kPa), and a load (24.11 KN). At the same time, the running distance until the bead portion was damaged was measured, and the value was displayed as an index with the conventional example being 100. The higher the value, the higher the durability.

[0028]

[Table 1]

As shown in the table, even when the bead filler was removed, the carcass cord did not suffer breakage damage, and it can be confirmed that the tire of the example can exhibit high bead durability as high as the conventional example.

[0030]

Since the present invention is configured as described above,
Even when the bead filler is eliminated, the breakage damage of the carcass cord can be effectively suppressed without reducing the cost and the productivity.

[Brief description of the drawings]

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

FIG. 2 is an enlarged sectional view showing a bead core together with a bead apex rubber.

FIGS. 3A to 3D are cross-sectional views showing another example of a bead apex rubber.

FIGS. 4A and 4B are diagrams illustrating a conventional technique.

[Explanation of symbols]

 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 9 Bead apex rubber 9A Main part 9B Wing part 11 Bead wire

Claims (2)

[Claims] 1. A pneumatic tire comprising a carcass folded around a bead core embedded in a bead portion from a tread portion to a side wall portion and a bead apex rubber extending radially outward from the bead core. The bead core is formed using a bead wire, and has a rectangular cross-section having a radially inward surface substantially in the tire axial direction, and the bead apex rubber extends radially from a radially outward surface of the bead core. A main portion extending outwardly, and wing portions extending radially inward in contact with the tire axially inward surface of the bead core and connected to the main portion, and further having a radius of the wing portion from the outward surface of the bead core. Direction length A
Is 0.3 to 1.0 times the cross-sectional height H of the bead core, and the thickness B of the wing portion from the inward surface is 0.3 to 1.0.
A pneumatic tire having a thickness of 1.5 mm. 2. The pneumatic tire according to claim 1, wherein said bead apex rubber has a durometer A hardness of 60 to 95 degrees.