JP2001018619A - Pneumatic tire excellent in bead part durability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve bead part durability by preventing causing separation on the winding end of a carcass ply, and moreover removing the possibility of fatigue failure in the bead part. SOLUTION: A carcass ply 1 is toroidally extended to a bead part 2 from a tread part via a side wall part, and also is wound back to the outer peripheral side from the inner peripheral side around a bead core 3 embedded in each bead part 2, to provide a winding part 4 wound on and along the peripheral surface of the core 3, to arrange one or more wire chafers 7 and 8 in the bead part 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having excellent bead portion durability, and more particularly to a heavy duty radial tire suitable for use in trucks, buses and the like.

[0002]

2. Description of the Related Art At least one carcass ply extending from a tread portion to a bead portion b through a sidewall portion to a bead portion b as shown in FIG. It is general that the c is wound around the bead core bc embedded in the bead portion b from the inside to the outside in the tire width direction and locked. Under such a bead portion structure, the load of the rim-assembled tire is reduced. During rolling, the bead portion on the radially outer side from the rim flange rf repeatedly undergoes deformation in a direction of falling outward in the tire width direction, so that stress is concentrated on the winding end of the carcass ply c, and as a result, As a result, there is a problem that separation of the winding end of the carcass ply is likely to occur.

In order to prevent the occurrence of such a winding end separation, for example, Japanese Patent Laid-Open No. 9-15631 has been proposed.
As disclosed in Japanese Patent Publication No. 0, it has been proposed to wrap a side portion of a carcass ply around a bead core and position its edge at a portion where distortion is small in the bead portion.

[0004]

However, according to such a proposed technique, the resistance of the bead portion to the collapse deformation as described above is reduced by eliminating the winding portion of the carcass unlike the prior art. To be smaller,
There is a problem that the fatigue of the bead outer surface portion in contact with a portion near the outer peripheral edge of the rim flange and the bead heel portion in contact with the base portion of the rim flange become particularly large, and the possibility of fatigue failure from those portions cannot be eliminated. there were.

The present invention advantageously solves such a problem and not only prevents separation at the winding end of the carcass ply, but also effectively eliminates the possibility of fatigue failure of the bead portion. And a pneumatic tire having excellent bead portion durability.

[0006]

The pneumatic tire of the present invention having excellent bead portion durability is generally made of a steel cord extending at an angle of about 70 to 90 ° with respect to the tire equatorial plane. At least one carcass ply
While extending toroidally from the tread portion to the bead portion through the sidewall portion, and wrapping around the bead core buried in each bead portion from the inner circumferential side to the outer circumferential side in the tire radial direction, a part of the wrapped portion Alternatively, all of them are provided with a winding portion wound around the bead core along the peripheral surface, and one or more wire chafers are arranged in the bead portion.

[0007] Here, the wire chafer refers to a bead portion reinforcing member made of a steel cord, and a region where the wire chafer is disposed can be any one of inside and outside in the tire width direction with respect to the bead core. It also includes the inner peripheral side of the bead core.

According to such a bead structure of a pneumatic tire, by winding the side portion of the carcass ply around the bead core, it is possible to prevent the separation of the winding end of the carcass ply from occurring. By arranging the required number of wire chafers in the required area and increasing the lateral stiffness of the bead, it is possible to effectively suppress the deformation of the bead from falling down in the tire width direction, such as when the tire is rolling. As a result, it is possible to sufficiently prevent the occurrence of fatigue failure in the contact portion of the bead portion with the rim flange or the like.

[0009] Preferably, the body portion of the carcass ply is sandwiched by a wire chafer in the thickness direction of the carcass ply, and preferably, the cord constituting the wire chafer is replaced with the cord and carcass constituting another wire chafer. The ply extends in a direction opposite to at least one of the cords constituting the ply.

[0010] According to the former, by sandwiching the carcass ply with two or more wire chafers, one wire chafer is arranged along the inside or outside of the carcass ply body in the tire width direction. The lateral rigidity of the bead portion can be further increased as compared with the case where the bead portion is provided, whereby the risk of fatigue failure of the bead portion can be more effectively removed, and the durability of the bead portion can be greatly improved. This is particularly true in the latter case, where the crossing of the cords between the wire chafers and / or between the wire chafers and the carcass ply can achieve a further increase in the bead stiffness.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view in the tire width direction showing one embodiment of the present invention for one bead portion. In the drawing, 1 indicates one carcass ply,
This carcass ply 1 extends toroidally from a tread portion (not shown) through a sidewall portion to a bead portion 2.
Consists of a steel cord extending at an angle of about 70-90 with respect to the tire equatorial plane.

Here, each side portion of the carcass ply 1 is wrapped around the bead core 3 buried in the bead portion 2 from the inner circumferential side to the outer circumferential side in the tire radial direction. A winding portion 4 is provided along the peripheral surface. In addition, in this figure, the case where the rewind portion is wound from the inside to the outside in the tire width direction is shown, but conversely, it is also possible to wind from the outside to the inside in the tire width direction. .

By the way, in such a winding of the rewinding portion, at least one portion of the winding portion 4 corresponding to the corner of the bead core 3 is plastically deformed, so that it is more accurately formed on the peripheral surface of the bead core. According to this, the winding portion 4 can be more effectively restrained by the bead core 3, and the risk of the carcass ply cord slipping out and separation of the winding portion can be advantageously removed.

Incidentally, such a plastically deformed portion is formed before the carcass ply is wrapped around one bead core 3.
It is preferable that the plastic deformation is formed in advance in a portion corresponding to the winding portion 4, whereby the intended plastic deformation can always be accurately performed, and the above-described effect can be further enhanced.

Here, preferably, the winding portion 4 is sandwiched between the bead core 3 and a bead filler 5 located on the outer peripheral side of the bead core 3. According to this, since the winding part 4 can be brought into close contact with the bead core 3 with the bead filler 5, pull-out of the ply cord and separation of the winding part 4 are both more advantageously prevented. .

Preferably, the winding portion 4 extends along the peripheral surface of the bead core beyond half the circumference of the cross-sectional profile of the bead core 3. As a general cross-sectional profile of the bead core 3,
There are polygons, circles, etc.
The above effect can be further enhanced by causing the winding portion 4 to extend along the bead core 3 beyond half the circumference of the cross-sectional profile.

Further, in the illustrated tire, at the bead portion 2, on the side opposite to the bead core 3 with respect to the carcass ply 1, from the inner peripheral portion of the bead core 3, the outer side in the tire width direction along the carcass ply 1. And two wire chafers 7 extending along the outer surface of the bead portion and reaching radially outward from the outer peripheral edge of the contact area with the rim flange 6.
In addition, two wire chafers 9 sandwiching the body portion 8 of the carcass ply 1 from the thickness direction of the carcass ply 1 inside the bead portion 2 in the tire width direction from the radially outer end of the bead filler 5. Although it is arranged in the inner peripheral area, it may be arranged further outward in the radial direction by the radially outer end of the bead filler. In this case, “Rim flange 6
The "contact area with" means the maximum contact area at the time of rolling load of the tire, which is the widest area.

According to such an arrangement of the wire chafers 7 and 9, the bead portion 2 is used for rolling the load of the tire.
In the action of the load on the tire, the wire chafer 7 disposed on the outer side in the tire width direction functions to suppress the rubber flow in the tire radial direction / width direction at the rim flange contact portion and suppresses the displacement in the tire equator direction. Make a move. The wire chafer 9 disposed outside in the tire width direction functions to suppress the bead portion from falling down to the outside in the tire width direction (to increase rigidity).

As a result, the lateral stiffness of the bead portion 2 is increased, and the deformation of the bead portion 2 falling outward in the tire width direction is effectively suppressed. Fatigue of the bead heel portion in contact with the outer surface portion and the base portion of the rim flange 6 can be sufficiently prevented, and bead portion durability can be greatly improved.

Here, the cords constituting the wire chafers 7, 9 are crossed each other between the two wire chafers 7, 9 and more preferably between the two wire chafers 7, 9 in addition to the carcass ply 1. When extending in mutually opposite directions, the wire chafers with intersecting angles
Since the deformation for suppressing the mutual movement is performed, the effect of suppressing the falling in the outside in the bead width direction increases.

1, one of the wire chafers 7 and 9 can be omitted. When the wire chafer 7 is omitted, for example, as shown in FIG. A radial inner end of one wire chafer 9 disposed between the main body portion 8 and the bead filler 5 is located near the bead core 3;
Positioning the inner end of the other wire chafer 9 in the radial direction along the inner peripheral side portion of the bead core 3 is not only for fixing the other wire chafer 9 with the bead core 3 but also for improving the effect of suppressing falling down. Is preferred.

FIG. 3 is a cross-sectional view showing a modified example shown in FIG. 2, in which the arrangement of the hard rubber portion 5a and the soft rubber portion 5b of the bead filter 5 is changed and the carcass ply 1 is wound. When the portion 4 is formed in a substantially elliptical shape, in the example shown in FIG. 3A, the other wire chafer 9 described in FIG. It has been wound up.

FIG. 3B shows an example shown in FIG.
In addition to the above, two additional reinforcing layers 10 made of an organic fiber cord, for example, a nylon fiber cord, are pressed from the inner peripheral portion of the bead core 3 outward in the tire width direction by pressing the other wire chafer 9. And extend it,
The radially outer end of the additional reinforcing layer 10 on the outer side in the tire width direction is located on the outer peripheral side of that of the other wire chafer 9.

In the example shown in FIG. 3 (c), in addition to arranging both wire chafers 9 as shown in FIG. 2, this also includes two additional reinforcing layers made of, for example, nylon fiber cords. 10 with respect to the bead core center line, the carcass ply winding part 4 and the other wire chafer 9
On the outer circumferential side, the bead is wound around the bead core 3 from the inner circumferential side to the outer circumferential side in the tire radial direction.

With any of these bead portion structures, separation of the carcass ply 1 winding portion is sufficiently prevented, and the possibility of fatigue failure of the bead portion 2 is advantageously eliminated to greatly improve the bead portion durability. Can be done.

[0026]

EXAMPLE A bead durability test was carried out on a drum for each of the example tires shown in FIGS. 3 and 4 and the conventional tire shown in FIG. 5, and the results are shown in Table 1 with indices. In addition, the larger the index value in the table, the better the result.

Here, the tire size is 285.
/60R22.5, rim width 9.00 × 22.5, filling air pressure 900 kPa and applied load 31
A large force was applied to the bead under the conditions of high internal pressure and overload at 50 kgf × 1.5, and the bead was run until the bead (outside of rubber) separated on the outer surface of the bead in contact with the rim flange.

[0028]

[Table 1]

According to the above Table 1, all of the example tires have much better bead durability than conventional tires due to the improved effect of preventing fatigue breakage in addition to the effect of preventing separation at the ply end. It is clear that.

[0030]

According to the present invention, at least one wire chafer is provided at the bead portion, particularly when the carcass ply is provided with a winding portion wound around the bead core along the peripheral surface thereof. By doing so, the lateral rigidity of the bead portion can be increased, and the durability can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a sectional view in a tire width direction showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view in the tire width direction showing another embodiment of the present invention.

FIG. 3 is a sectional view in a tire width direction showing a modification of FIG. 2;

FIG. 4 is a sectional view in the tire width direction showing an example tire.

FIG. 5 is a sectional view in the tire width direction showing a conventional structure.

[Explanation of symbols]

 Reference Signs List 1 carcass 2 bead portion 3 bead core 4 winding portion 5 bead filler 5a hard rubber portion 5b soft rubber portion 6 rim flange 7,9 wire chafer 8 main body portion 10 additional reinforcing layer

Claims (3)

[Claims] At least one carcass ply made of a steel cord is toroidally extended from a tread portion through a sidewall portion to a bead portion,
Around the bead core buried in each bead portion, rewind from the inner peripheral side in the tire radial direction to the outer peripheral side, and a part or all of the rewind portion is provided with a winding portion wound around the bead core along the peripheral surface. A pneumatic tire having excellent durability in a bead portion, wherein one or more wire chafers are disposed in the bead portion. 2. The pneumatic tire according to claim 1, wherein the body member of the carcass ply is sandwiched by a wire chafer in the thickness direction thereof. 3. A code constituting a wire chafer,
The pneumatic tire having excellent bead portion durability according to claim 1 or 2, wherein the pneumatic tire is extended in a direction opposite to at least one of a cord constituting another wire chafer and a cord constituting a carcass ply.