JPH10329514A - Radial tyre for heavy load - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the durability of a bead part further, in the radial tyre for a heavy load. SOLUTION: A wire chafer 20 consisting of wire cords 22 is arranged on the opposite side to the bead core 12 side of a carcass ply 14. By making the angle of the wire cord 22 for a tyre periphery direction to 17 deg.-23 deg. which is a smaller angle than the past, a creep generated on the first rubber chafer 24 of the outside of the wire chafer 20 by a rim reaction force can be restrained. As the 100% tensile stress of the first rubber chafer 24 is made to 5.88 Mpa, the durability of the first rubber chafer 24 is improved much more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heavy duty radial tire used for heavy duty vehicles such as trucks, buses and light trucks, and more particularly to a heavy duty radial tire having a high durability of a bead portion.

[0002]

2. Description of the Related Art In a heavy-duty radial tire used for trucks, buses, light trucks, etc., in order to increase the durability of a bead portion, a wire reinforcing layer is provided outside a carcass ply around a bead core, or a contact surface with a rim is provided. Has a rubber chafer.

[0003] Conventionally, in order to suppress the creep of the rubber chafer, the shape of the bead portion has been improved. In particular, even among tubeless heavy load radial tires, 15 ° deep bottom rims (15
For (DC) tires, various shapes of bead portions have been proposed. In the 15 ° deep-bottom rim, the bead seat portion is tapered at 15 ° to strengthen tightness due to internal pressure and seal the internal pressure at the bottom of the bead.

[0004]

By the way, although the durability of the bead portion has been improved by various improvements, some tires may be used for a long time by replacing the tread like a retreaded tire. It is desired to further suppress deformation of the bead portion due to rubber chafer creep during running, failure of the bead portion, and the like.

Further, a cord with a spiral has conventionally been used as a wire cord of a wire reinforcing layer.
However, since the cord with a spiral has a high bending rigidity, it has a strong force to return to an original straight state after bending. Therefore, the wire reinforcing layer adhered along the curved surface of the carcass ply may float from the carcass in an attempt to return to the original flat state.

An object of the present invention is to provide a heavy-duty radial tire capable of solving the above problems in consideration of the above facts.

[0007]

Conventionally, the angle of the wire cord of the wire reinforcing layer with respect to the tire circumferential direction has been set to about 30 °. This is in consideration of reinforcement of the entire bead portion and prevention of separation generated from the end of the wire cord on the outer side in the tire width direction.

As a result of various experiments and studies by the inventor, the creep generated in the rubber outside the wire reinforcing layer in the bead portion is due to rubber flow in the tire radial direction due to the rim reaction force. It was found to worsen with increasing. Further, in recent years, coating rubber used for the wire reinforcing layer has been variously improved, and it has been found that even when the angle of the wire cord is set to 20 ° or less, separation does not occur from the end of the wire cord.

The radial tire for heavy load according to the present invention is made in view of the above-mentioned facts, and a pair of bead cores and a portion near an end in the width direction are folded around the bead core from the inside to the outside of the tire. A carcass ply to be locked, and a wire reinforcing layer having a plurality of wire cords arranged in parallel and arranged on a side opposite to the bead core side of the carcass ply, and the wire cords in the tire circumferential direction. Is 17 ° to 23 °.

The operation of the radial tire for heavy load according to the first aspect will be described. Since the angle of the wire cord of the wire reinforcing layer for reinforcing the bead portion is set to an angle of 17 ° to 23 °, which is smaller than the conventional angle, creep generated in the rubber outside the wire reinforcing layer due to the rim reaction force can be suppressed. Also, the durability of the bead portion can be improved.

According to a second aspect of the present invention, in the heavy load radial tire according to the first aspect, the wire cord does not have a spiral structure.

The operation of the heavy duty radial tire according to the second aspect will be described. Since the wire cord of the wire reinforcing layer does not have a spiral structure, the cord bending rigidity is lower than that of a conventional wire cord employing a spiral structure.
For this reason, the force to return to the original straight state after bending along the carcass ply is weak, so that the wire reinforcing layer does not float from the carcass.

[0013] Here, the spiral structure refers to a structure in which a spiral filament is spirally wound around the outer periphery of a steel cord.

According to a third aspect of the present invention, in the heavy-duty radial tire according to the first or second aspect, the wire reinforcing layer has an outer end in the tire width direction outside the folded end of the carcass ply. It is located inside the tire radial direction, and the end in the tire width direction is located inside the tire width direction inside a perpendicular line passing through the center of the bead core and perpendicular to the bead seat of the rim. .

The operation of the heavy duty radial tire according to the third aspect will be described. The reinforcing effect is most exerted by disposing the wire reinforcing layer from a position corresponding to the upper end of the rim flange having a high rim reaction force (contact pressure with the rim) to a position immediately below the center of the bead core. In addition, when the end of the wire reinforcing layer on the inner side in the tire width direction does not pass through the center of the bead core and is not located on the inner side in the tire width direction beyond a perpendicular perpendicular to the bead sheet of the rim, the reinforcing effect is reduced. You.

Further, since the outer end of the wire reinforcing layer in the tire width direction is arranged on the inner side in the tire radial direction from the folded end of the carcass ply, the outer end of the wire reinforcing layer in the tire width direction at the time of deformation of the tire and the periphery thereof are arranged. Relative movement with respect to the rubber can be reduced, and thereby the occurrence of separation from the outer end in the tire width direction can be suppressed.

According to a fourth aspect of the present invention, in the heavy-duty radial tire according to any one of the first to third aspects, a 100% tensile stress outside the wire reinforcing layer is 4.90 to 4.0%. 6. A rubber chafer of 90 Mpa is arranged.

Here, the measuring method of the tensile stress is based on JIS
K 6251-1993. The operation of the heavy duty radial tire according to claim 4 will be described.

Since the rubber chafer having a 100% tensile stress of 4.90 to 6.90 Mpa is arranged outside the wire reinforcing layer, creep of the rubber chafer due to the rim reaction force can be suppressed.

When the 100% tensile stress of the rubber chafer is less than 4.90 Mpa, creep due to rim reaction force increases and durability is insufficient.

On the other hand, when the 100% tensile stress of the rubber chafer exceeds 6.90 Mpa, breakage tends to occur when the rim is attached or detached due to a decrease in elongation due to thermal deterioration.

According to a fifth aspect of the present invention, in the radial tire for heavy loads according to any one of the first to fourth aspects, the bead portion is formed for a 15 ° deep rim. Features.

The operation of the heavy load radial tire according to the fifth aspect will be described. The radial tire for heavy load of the present invention can be mounted on the 15 ° deep rim because the bead portion is formed for the 15 ° deep rim.

The combination of the heavy load radial tire for the 15 ° deep bottom rim and the 15 ° deep bottom rim is a combination having a particularly high contact pressure with the rim, that is, a high rim reaction force. However, the heavy-duty radial tire of the present invention can suppress the creep of the rubber at the bead portion due to the rim reaction force. Become.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the heavy duty radial tire according to the present invention will be described with reference to FIGS.

As shown in FIG. 1, the heavy duty radial tire 10 according to the present embodiment mounted on a 15 ° deep bottom rim 18
Is a pair of bead cores 12 (only one side is shown in FIG. 1)
And a carcass ply 14 that straddles a pair of bead cores 12 in a toroidal manner. The carcass ply 14 has a carcass ply cord extending in the radial direction.

Although not shown, a belt and a tread rubber are arranged outside the carcass ply 14 in the tire radial direction, similarly to a normal heavy load radial tire.

Both ends in the width direction of the carcass ply 14 are folded from the inside to the outside of the tire around the bead core 12 having a hexagonal cross section.

Inside the bead portion 16, a wire chafer 20 is arranged on the side of the carcass ply 14 opposite to the bead core 12 side.

The end 20A of the wire chafer 20 on the outer side in the tire width direction (in the direction of arrow A) is a carcass ply 1
4 is located radially inward (in the direction of arrow B) with respect to the folded end 14A.

On the other hand, the end 20B of the wire chafer 20 on the inner side in the tire width direction (the side opposite to the direction of arrow A).
Is a 15 ° deep rim 1 passing through the center of the bead core 12
8 is located on the inner side in the tire width direction than the perpendicular S perpendicular to the bead sheet 18A.

The wire chafer 20 is formed by arranging wire cords 22 having no spiral in parallel to form a cord, and applying a rubber coating to the cord. In the present embodiment, the structure of the wire cord 22 is 3 + 8 ×
0.125, and the number of shots is 25 lines / 5 cm.

As shown in FIG.
Is an angle θ with respect to the tire circumferential direction (direction of arrow C) of 17
To 23 °, and in the present embodiment, the angle θ is set to 20 °.

As shown in FIG. 1, a first rubber chafer 24 is arranged on the outer peripheral portion of the bead portion 16 from a position inside the perpendicular line S in the tire width direction toward the sidewall. A second rubber chafer 26 is arranged inside the first rubber chafer 24 in the tire width direction.

In this embodiment, the 100% tensile stress of the first rubber chafer 24 is changed to the second rubber chafer 26.
Is set higher than the 100% tensile stress of the first rubber chafer 24, and the 100% tensile stress of the first rubber chafer 24 is 5.88M.
and the 100% tensile stress of the second rubber chafer 26 is 1.96 Mpa.

The second rubber chafer 26 has a small creep input in position, a large deformation input when attaching and detaching the rim, and is required to have a larger elongation than a stress.

Next, the operation of the present embodiment will be described. Fifteen
The combination of the heavy load radial tire 10 and the deep 15 ° deep rim 18 of the present embodiment, which is for deep rims, is a combination having a particularly high contact pressure with the rim, that is, a high rim reaction force. In the heavy duty radial tire 10, since the angle of the wire cord 22 is set to an angle of 17 ° to 23 °, which is smaller than the conventional angle, creep occurring in the first rubber chafer 24 outside the wire chafer 20 due to the rim reaction force is suppressed. it can.

Since the 100% tensile stress of the first rubber chafer 24 is set to 5.88 Mpa, the durability of the first rubber chafer 24 is further improved.

Since the wire cord 22 having no spiral structure has a smaller bending rigidity than the wire cord having the spiral structure, the bending rigidity of the wire chafer 20 is also smaller. Therefore, the wire chafer 20 attached to the outer surface of the carcass ply 14 does not float off the carcass ply 14.

Further, since the end portion 20A of the wire chafer 20 is disposed radially inward of the folded end 14A of the carcass ply 14, the end portion 20A of the wire chafer 20 and the surrounding rubber when the tire is deformed are deformed. The relative movement can be reduced, and the occurrence of separation from the end 20A can be suppressed.

Next, FIG. 3 is a graph showing the relationship between the angle θ of the wire cord of the wire chafer with respect to the circumferential direction of the tire, the amount of tire deformation, and the length of a crack (separation) generated from the end of the wire chafer. To

Measuring method of tire deformation: As shown in FIG. 4, the depth D of the concave portion at the contact portion with the rim flange (after running a certain distance) was measured.

A method for measuring the length of a crack generated from the end of the wire chafer: As shown in FIG. 5, the linear distance L from the end 20A of the wire chafer 20 to the tip of the crack 100 is measured along the wire cord 22. It was measured.

From the graph shown in FIG. 3, in order to suppress the deformation of the tire and the crack generated from the end of the wire chafer, the angle θ of the wire cord 22 with respect to the tire circumferential direction is set to 17 ° to 23 °. It turns out to be desirable.

[0045]

As described above, the radial tire for heavy load according to the first aspect has the above-described configuration, and therefore has an excellent effect that bead failure due to rim reaction force can be suppressed as compared with the related art. Have.

The heavy-duty radial tire according to claim 2 has the above-described configuration, and thus has an excellent effect that the inner surface of the wire reinforcing layer can be prevented from floating.

According to the third aspect of the present invention, the radial tire for heavy load has the above-described structure, so that the effect of reinforcing the bead portion of the wire reinforcing layer can be maximized, and the separation from the outer end of the wire reinforcing layer in the tire width direction. It has an excellent effect that generation can be suppressed.

The heavy-duty radial tire according to the fourth aspect has the above-described configuration, and thus has an excellent effect that creep of the rubber chafer due to the rim reaction force can be suppressed.

In addition, since the radial tire for heavy load according to the fifth aspect has the above-described configuration, it can be mounted on a 15 ° deep rim, and the effect of the present invention is most exhibited.

[Brief description of the drawings]

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

FIG. 2 is a plan view of a wire reinforcing layer.

FIG. 3 is a graph showing a relationship between an angle of a wire cord, a tire deformation amount, and a crack length at a wire end.

FIG. 4 is an explanatory diagram illustrating a method of measuring a tire deformation amount.

FIG. 5 is an explanatory diagram illustrating a method for measuring the length of a crack generated from the end of a wire chafer.

[Explanation of symbols]

 Reference Signs List 10 radial tire for heavy load 12 bead core 14 carcass ply 18 15 ° deep bottom rim 18A bead sheet 20 wire chafer (wire reinforcing layer) 22 wire cord 24 first rubber chafer

Claims (5)

[Claims] A pair of bead cores, a carcass ply whose width direction end portion is folded back around the bead core from the inside to the outside of the tire and is locked, and the carcass ply is arranged on a side opposite to a bead core side, A wire reinforcing layer having a plurality of wire cords arranged in parallel, wherein the angle of the wire cords with respect to the tire circumferential direction is 17 °.
A heavy-load radial tire characterized in that the angle is set to 23 °. 2. The heavy duty radial tire according to claim 1, wherein the wire cord has no spiral structure. 3. The wire reinforcing layer has an outer end in the tire width direction located radially inward of the folded end of the carcass ply, and an inner end in the tire width direction passing through the center of the bead core. The heavy-duty radial tire according to claim 1, wherein the radial tire is located inside a perpendicular line perpendicular to a bead seat of the rim in a tire width direction. 4. A rubber chafer having a 100% tensile stress of 4.90 to 6.90 Mpa is arranged outside the wire reinforcing layer. The radial tire for heavy load described. 5. The heavy duty radial tire according to claim 1, wherein the bead portion is formed for a 15 ° deep bottom rim.