JP2000301918A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a separation trouble inside a bead part from being generated, so as to enhance durability of the bead part. SOLUTION: A carcass layer 16 winds a terminal part 16C in along an outer circumference of a bead core 12 substantially free from generation of deformation at the time of loaded rotation to prevent a separation trouble of rubber which starts at the terminal part 16C as a start point. In a bead reinforcing layer 18, a tangential line L3 connected to a central line of the layer 18 in a terminal part 18B in a tire-axis-directional outside of the layer 18 is set in parallel to a tangential line L2 connected to a central line of a body part 16A in an intersection point D of a perpendicular L1 extended from a terminal part 18B toward the body part 16A of the carcass layer 16 intersected with the central line of the body part 16A. Since a compressive direction at the time of loaded rotation comes to a diagonal direction with respect to a code of the terminal part 18B, generation of a compressive strain generated in the part 18B is moderated to prevent separation from being generated.

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 more particularly to a pneumatic radial tire having improved durability of a bead portion.

[0002]

2. Description of the Related Art In a pneumatic radial tire used for trucks and the like, particularly used under heavy load, and after being worn, the tread is rehabilitated and used a plurality of times, a stress concentration portion of a reinforcing cord end of a carcass layer is used by long-term use. There is a problem that separation occurs in the rubber from the starting point and the tire cannot be used.

That is, in a tire used by filling a high internal pressure, such as a tire for a truck or a bus, the carcass layer tends to be pulled out from the bead core by air pressure, and a large stress concentration occurs at the terminal portion. Is repeatedly deformed, thereby causing a separation failure starting from the terminal portion.

In order to cope with such a separation failure at the end of the carcass, many techniques such as disposing a bead reinforcing layer outside the carcass layer, disposing a rubber member at the bead, and further forming a carcass have been proposed. ing.

[0005]

In recent years, the use conditions of large tires for trucks and buses have become severer due to an increase in the number of times of rehabilitation in consideration of the environment and economy. In the tire having a low flatness, the durability of the bead deteriorates. Therefore, even if the conventional technique is used, the prevention of the separation failure in the bead portion is not sufficient, and the fundamental solution to the failure of the bead portion has not been reached.

The present invention has been made in view of the above circumstances, and has as its object to provide a pneumatic radial tire having excellent bead durability and suitable for heavy-duty vehicles.

[0007]

According to a first aspect of the present invention, there is provided a main body extending from a bead core of one bead to a bead core of the other bead, and a main body provided continuously with the main body. A carcass comprising at least one carcass layer composed of a plurality of steel cords extending substantially in the radial direction having a winding portion wound along the outer periphery; and a carcass provided at a tire radial outside of the carcass, A belt that reinforces the crown of the carcass, comprising a plurality of cords inclined with respect to the radial direction, and arranged around the bead core outside the tire of the carcass layer. A perpendicular line extending from a terminal portion of the bead reinforcing layer on the outer side in the tire axial direction toward the body portion of the carcass layer. To a tangent of the body portion at the intersection between the body portion, the tangent of the bead reinforcing layer in the tire axial direction outer side of the end portion of the bead reinforcing layer,
It is characterized by being parallel or inclined to the outside of the tire.

Next, the operation of the pneumatic radial tire according to the first aspect will be described.

In the pneumatic radial tire according to the present invention, the carcass layer is formed by plastic deformation and is wound around the outer peripheral surface of the bead core, so that the terminal portion, which is a source of stress concentration, hardly deforms at the time of load rolling. By arranging it on the upper side, the separation failure originating from the terminal portion of the carcass layer is fundamentally eliminated.

In addition, since the bead reinforcing layer is arranged outside the tire of the carcass layer and around the bead core, it is possible to prevent abrasion of the tire outer skin due to friction with the rim flange during rolling.

A terminal portion of the bead reinforcing layer is disposed in the bead portion, and a terminal portion of the bead reinforcing layer on the outer side in the tire axial direction becomes a source of stress concentration similar to the carcass layer terminal portion of the conventional tire.

That is, when the bead portion bends in the rim flange direction during load rolling, the main body portion of the carcass layer radially outward from the vicinity of the end portion of the bead reinforcing layer sinks inward in the tire radial direction. In order to make such a deformation, a large compressive strain is generated in the end portion of the bead reinforcing layer.

At this time, in the arrangement in which the vicinity of the end portion of the bead reinforcing layer is inclined so as to approach the main body portion of the carcass layer, compressive deformation is more likely to occur directly at the end portion.

Here, in the present invention, the inclination of the terminal portion of the bead portion reinforcing layer is equal to (ie, parallel to) the inclination of the main portion of the carcass layer, or the terminal portion is inclined more outward in the tire axial direction. Therefore, even if the main body of the carcass layer sinks and deforms during load rolling, it is possible to greatly reduce the occurrence of compressive strain generated at the bead reinforcing layer terminal portion, thereby starting from the bead reinforcing layer terminal portion. The occurrence of separation can be prevented.

Further, unlike the end portion of the carcass layer, the end portion of the bead reinforcing layer is hardly subjected to the force of being pulled out by the internal pressure. Unlike the carcass layer where the folded part is not adjacent and the cord is inclined with respect to the radial direction, the cord in the bead reinforcing layer changes angle even when the bead deforms during load rolling By doing so, the stress concentration is reduced by alleviating the compressive strain generated at the cord end, but even if the carcass layer main body sinks by further inclining the end, the compressive deformation at the end hardly occurs By doing so, the durability of the bead portion is greatly improved.

According to a second aspect of the present invention, in the pneumatic radial tire according to the first aspect, a distance between a terminal portion of the bead reinforcing layer on the outer side in the tire axial direction and the main body portion is set to
The maximum width measured in parallel with the bead base of the bead core is 1.2 times or less.

Next, the operation of the pneumatic radial tire according to claim 2 will be described.

In order to alleviate the compressive strain at the terminal portion of the bead reinforcing layer, the distance between the terminal portion of the bead reinforcing layer and the main body of the carcass layer is excessively increased to increase the inclination of the bead reinforcing layer. Since the thickness of the rubber in the above increases, the heat generation of the bead portion increases, which adversely affects the durability. Therefore, the distance between the end portion of the bead reinforcing layer and the main body of the carcass layer is 1.2 times the maximum width of the bead core. It is preferable to suppress it to twice or less.

According to a third aspect of the present invention, in the pneumatic radial tire according to the first or second aspect, the cord of the bead reinforcing layer has a width of 30 in the radial direction.
It is characterized by being inclined at an angle in the range of degrees to 80 degrees.

Next, the operation of the pneumatic radial tire according to claim 3 will be described.

It is preferable that the cord of the bead reinforcing layer is inclined at an angle in the range of 30 to 80 degrees with respect to the radial direction. When the angle of the cord is less than 30 degrees, the carcass body falls down. At that time, as it approaches the tire radial direction like the steel cord of the carcass layer,
Strain relaxation at the end of the bead reinforcing layer due to a change in the angle of the cord of the bead reinforcing layer hardly occurs, and a large concentration of compressive stress occurs at the end of the cord.

On the other hand, if the angle of the cord exceeds 80 degrees,
Since the bead reinforcement cords are oriented almost in the circumferential direction, the shear stiffness of the bead reinforcement layer is reduced, and the effect of the bead on circumferential shear deformation, in which the sidewalls are displaced in the rotation direction due to kicking when the tire rolls, is greatly improved. Therefore, wear due to circumferential displacement between the rim flange and the tire outer skin cannot be effectively prevented, and the role as a bead reinforcing layer cannot be sufficiently exhibited.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a pneumatic radial tire 10 of the present embodiment includes a pair of bead cores 12.
(Only one side is shown in FIG. 1), and a carcass 14 that straddles a pair of bead cores 12 in a toroidal shape.

In the present embodiment, the carcass 14 is composed of one carcass layer (carcass ply) 16, but the number of carcass layers 16 may be two or more.

The carcass layer 16 includes a plurality of steel cords (not shown) extending in a substantially radial direction (preferably within ± 10 ° with respect to the radial direction) arranged in parallel with each other. It has a normal structure in which a plurality of steel cords are embedded in a thin coating rubber (not shown).

The carcass layer 16 extends from the bead core 12 of one bead portion 11 to the bead core 1 of the other bead portion 11.
2 and a winding portion 16 </ b> B wound along the outer periphery of the bead core 12.

The position of the terminal portion 16C of the winding portion 16B of the carcass layer 16 is located on the upper side of the bead core 12 at least inside the tire axial direction outside end of the bead core 12 in the tire axial direction. It is preferably located on the inner side in the tire axial direction from the center, and is further located near the main body portion 16A as shown in FIG. 1 (that is, the carcass layer 16 makes substantially one round around the bead core 12). preferable.

The steel cord of the winding part 16B is as follows.
In the tire manufacturing stage (at least before vulcanization), at least one or more portions are plastically deformed along the outer peripheral surface of the bead core 12, and the steel cord in the product tire is used to return to a straight state. Has not occurred.

Outside the tire of the carcass layer 16, a bead reinforcing layer (so-called chafer) 18 is arranged around the bead core.

The bead reinforcing layers 18 are parallel to each other,
A plurality of cords (not shown) inclined at an angle in the range of 30 to 80 degrees with respect to the radial direction are covered with rubber. The cord used for the bead reinforcing layer 18 may be a steel cord or an organic fiber cord such as nylon.

Here, the bead reinforcing layer 18 is disposed adjacent to the bead core 12 along the outer peripheral surface of the carcass layer 16 from the bead core 12 to the terminal portion 18A on the inner side in the tire axial direction. The outer end portion 18 </ b> B extends linearly in a direction away from the bead core 12.

The bead reinforcing layer 18 is formed of the bead reinforcing layer 1
8 and the carcass layer 1 from the terminal portion 18B on the outer side in the tire axial direction.
6 and a vertical line L1 extending toward the main body 16A and the main body 1
With respect to a tangent line L2 drawn to the center line of the main body 16A at the intersection D with the center line of 6A, the bead reinforcing layer 18 at the end portion 18B of the bead reinforcing layer 18 on the outer side in the tire axial direction.
A tangent line L3 drawn to the center line is set in parallel.

Further, in the bead portion 11, the distance S between the center line of the terminal portion 18 B outside the bead reinforcing layer 18 in the tire axial direction and the center line of the main body portion 16 A is set to the bead base 11.
It is preferable to set the maximum width W of the bead core 12 measured in parallel to A to be 1.2 times or less.

The bead portion 11 has a bead core 12
Stiffener 2 that secures the rigidity of bead portion 11 on the tire radial outside of winding portion 16B of carcass layer 16 wound around
0 is provided. Stiffener 20 of the present embodiment
Is composed of a stiffener 20A and a stiffener 20B.

A relatively hard rubber is used for the stiffener 20A to suppress the deformation of the bead portion 11. On the other hand, the stiffener 20B has a bead reinforcing layer 18.
Of distortion near the terminal portion 18B of the stiffener 20A
Stiffener 2 to prevent cracks from growing directly inside
Rubber different from OA is used.

The structure of the stiffener 20 is not limited to that of the present embodiment. As shown by a two-dot chain line in the figure, the stiffener 20A is connected to the hard stiffener 20Aa on the bead core 12 side and the outer side in the tire radial direction. The stiffener 20B may be made of the same rubber as the soft stiffener 20Ab (that is, the stiffener 20B and the soft stiffener 2A).
0Ab is integrated. ).

Although not shown, a belt for reinforcing the crown portion of the carcass 14 is provided outside the carcass 14 in the tire radial direction. (Operation) In the pneumatic radial tire 10 of the present embodiment, the steel cord of the carcass layer 16 is habitated by plastic deformation and wound around the outer peripheral surface of the bead core 12,
Since the end portion 16C, which is a source of stress concentration, is arranged so as to be in contact with the bead core 12 which hardly deforms during load rolling, separation failure of rubber in the bead portion 11 starting from the end portion 16C of the carcass layer 16 is prevented. can do.

The bead reinforcing layer 18 disposed outside the carcass layer 16 on the tire is provided with a rim flange 2 at the time of rolling.
2 prevents wear of the tire skin due to rubbing with 2.

Further, at the time of load rolling, as shown in FIG. 2, when the bead portion 11 bends in the direction of the rim flange 22 (from the state shown by the solid line to the state shown by the two-dot chain line), the bead reinforcing layer Although the body portion 16A of the carcass layer 16 is deformed to sink inward in the tire radial direction from the vicinity of the terminal portion 18A of the tire 18, in the present embodiment, the inclination of the bead reinforcing layer 18 near the terminal portion 18B is reduced. Is equal to (that is, parallel to) the inclination of the main body 16A of the carcass layer 16, even if the main body 16A of the carcass layer 16 sinks and deforms during load rolling, the compression direction is as shown by the arrow A. Bead reinforcing layer 1 in the terminal portion 18B
Since it is oblique to the code 8 (not shown),
The occurrence of compressive strain (compression direction is the direction of arrow A shown in FIG. 2) generated in the terminal portion 18B of the bead reinforcing layer 18 can be greatly reduced. For this reason, it is possible to prevent the occurrence of separation from the terminal portion 18B of the bead reinforcing layer 18 as a starting point.

Further, the terminal portion 18B of the bead reinforcing layer 18
The side of the bead reinforcing layer 18 is hardly subjected to the force to be pulled out by the internal pressure, and the end portion 18B of the bead reinforcing layer 18 differs from the conventional tire in that the winding portion 16B of the carcass layer 16 (corresponding to the folded portion of the carcass layer of the conventional tire). ) Are not adjacent to each other, and the cords are inclined with respect to the radial direction. Therefore, even when the bead portion 11 is bent and deformed at the time of load rolling, the cords in the bead reinforcing layer 18 are hardly changed in angle.
This deformation alleviates the concentration of the compressive stress in the radial direction of the terminal portion 18B.

The distance S between the end portion 18B of the bead reinforcing layer 18 and the main body portion 16A is equal to the maximum width W of the bead core 12.
Exceeds 1.2 times of the end portion 18 of the bead reinforcing layer 18.
The thickness of the rubber near B increases, and the heat generation of the bead portion 11 increases, which may adversely affect the durability.

When the angle of the cord of the bead reinforcing layer 18 with respect to the radial direction is less than 30 degrees, when the main body 16A of the carcass layer 16 falls down,
As the steel cord approaches the tire radial direction, distortion of the bead reinforcement layer 18 at the end portion 18B is unlikely to occur due to a change in the cord angle of the bead reinforcement layer 18, and a large concentration of compressive stress directly at the cord end. Occurs.

On the other hand, when the angle of the cord exceeds 80 degrees,
Since the shear stiffness of the bead reinforcing layer 18 is reduced and the effect of suppressing circumferential shear deformation generated at the time of rolling of the tire at the bead portion 11 is reduced, wear due to circumferential displacement between the rim flange 22 and the tire skin is effectively prevented. It cannot be prevented. (Other Embodiments) The bead reinforcing layer 18 of this embodiment
Is a terminal portion 18 outside the bead core 12 in the tire axial direction.
At B, it extended linearly (tangential to the outer peripheral surface of the carcass layer 16) in a direction away from the bead core 12, but
The present invention is not limited to this. As shown in FIG. 3, as shown in FIG. 3, an arc-shaped portion having a radius R outside the tire is bent in the vicinity of the bead core 12, and the outer end portion 18 </ b> B is linearly formed. In addition, it may be parallel to the tangent line L2, and as shown in FIG. 4, may be inclined so that a linear portion near the terminal portion 18B opens to the outside of the tire. (Test Example) Next, in order to confirm the effect of the present invention, a conventional tire having a tire size of 285 / 60R22.5 and a tire of the embodiment to which the present invention was applied were prepared, and an indoor drum test was performed. Endurance test was performed on the tire.

The tire of the first embodiment has the structure shown in FIG. 1, the tire of the second embodiment has the structure shown in FIG. 3, the tire of the third embodiment has the structure shown in FIG. It is a tire of the structure shown in FIG.

As shown in FIG. 5, the conventional tire has a structure in which the folded portion 16D of the carcass layer 16 approaches the main body 16A toward the outside in the tire radial direction.

Each of the carcass layers of the tires of Examples 1 to 3 and the conventional example was (1 × 3 + 9 + 15) × 0.175 mm +
A steel cord having a structure of 1 × 0.15 mm was arranged in parallel at a density of 26 wires per 5 cm (measurement site: around the bead core) and covered with rubber, and the cord direction was substantially set in the radial direction.

Each of the bead reinforcing layers of the tires of Examples 1 to 3 and the conventional example was (1 × 3 + 9 + 15) × 0.175 mm
A steel cord having a structure of + 1 × 0.15 mm is arranged in parallel at a density of 21 wires per 5 cm (measurement site: around the bead core) and covered with rubber, and the cord direction is inclined at 60 degrees to the radial direction. Yes (measurement site:
Terminal portion on the outside in the tire axial direction)

In the tire of Example 1, the distance S / the maximum width W was 1.3 times, and in the tire of Example 2, the distance S /
The maximum width W is 1.0 times, and in the tire of Example 3, the distance S / the maximum width W is 1.0 times.

In the drum test, an internal pressure of 900 k was applied to the test tire.
After filling with Pa, the steel sheet was pressed on a steel drum having a radius of 1.7 m with a load of 5200 kg, and allowed to run at a speed of 60 km / h until a bead failure (separation) occurred.
The room temperature at that time was 46 ° C.

The evaluation was performed by measuring the running distance until a bead failure occurred, and expressed as an index with the reciprocal of the running distance until the bead failure occurred in the conventional tire as 100. It should be noted that the larger the value, the longer the traveling distance until the bead failure occurs, and the more excellent the durability of the bead.

[0051]

[Table 1]

As a result of the test, Example 1 to which the present invention was applied
In the tires Nos. 1 to 3, it was found that the running distance until separation occurred in the bead portion was greatly extended, and the durability of the bead portion was greatly improved.

For this reason, it is understood that the pneumatic radial tire to which the present invention is applied is suitable for use as a base tire of a retreaded tire.

In the conventional tire, when the load rolls and the bead portion 11 undergoes bending deformation in which it falls down, the compression direction is indicated by an arrow A as shown in FIG.
In the code direction with respect to the terminal portion 16C, a large compressive strain occurs near the terminal portion 16C of the carcass layer 16.

[0055]

As described above, the pneumatic radial tire of the present invention has the above-mentioned structure, and therefore has an excellent effect that the durability of the bead portion can be improved.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view showing how a bead portion of the pneumatic radial tire shown in FIG. 1 is deformed. It is sectional drawing of the bead part of the conventional pneumatic radial tire used for the test.

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

FIG. 4 is a sectional view of a bead portion of a pneumatic radial tire according to still another embodiment of the present invention.

FIG. 5 is a sectional view of a bead portion of a pneumatic radial tire according to a conventional example used for a test.

[Explanation of symbols]

 Reference Signs List 10 pneumatic radial tire 11 bead portion 12 bead core 14 carcass 16 carcass layer 16A main body portion 16B winding portion 16C terminal portion 18 bead reinforcing layer 18B terminal portion L1 perpendicular L2 tangent L3 tangent W maximum width S distance

Claims (3)

[Claims] 1. A body having a main body extending from a bead core of one bead part to a bead core of the other bead part, and a winding part provided continuously with the main body part and wound along an outer periphery of the bead core. Air comprising: a carcass composed of at least one carcass layer composed of a plurality of steel cords extending in a radial direction; and a belt provided radially outside the carcass in a tire radial direction and reinforcing a crown portion of the carcass. An inner radial tire, comprising a plurality of cords inclined with respect to a radial direction, comprising a bead reinforcing layer disposed around the bead core outside the tire of the carcass layer, and a tire shaft of the bead reinforcing layer. The book at the intersection of a perpendicular extending from the terminal part on the outside in the direction toward the main part of the carcass layer and the main part. A pneumatic radial tire, wherein a tangent line of the bead reinforcement layer at a terminal portion of the bead reinforcement layer on the outer side in the tire axial direction with respect to a tangent line of the body portion is parallel or inclined to the outside of the tire. 2. The distance between a terminal portion of the bead reinforcing layer on the outer side in the tire axial direction and the body portion is 1.2 times or less a maximum width measured in parallel with a bead base of the bead core. The pneumatic radial tire according to claim 1, wherein: 3. The pneumatic device according to claim 1, wherein the cord of the bead reinforcing layer is inclined at an angle in a range of 30 to 80 degrees with respect to a radial direction. Radial tire.