JP2002079813A - Run-flat tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new run-flat tire. SOLUTION: This run-flat tire is provided with a carcass 6 extending from a tread part 2 to a bead core 5 through a sidewall part 3. The bead core 5 has a shape longer than it is wide, and an inner surface 5i in a tire radius direction thereof is placed adjacently to a bead bottom surface 4b, and an outer surface 5o thereof is placed at 30% to 60% height of a tire section height H.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a run flat tire capable of running continuously even during a puncture.

[0002]

2. Description of the Related Art Various types of so-called run flat tires have been proposed which enable the vehicle to continue running even when air leaks from the tire due to puncture or the like. For example, in Japanese Patent Application Laid-Open No. Hei 5-155,099, a rubber layer having a substantially crescent cross section is arranged inside the sidewall portion of the tire to reduce the vertical deflection of the tire at the time of puncture or the like, thereby suppressing the structural destruction of the tire. ing.

However, the run-flat tire having such a rubber layer having a substantially crescent shape in cross section has a structure in which the rigidity of almost the entire region of the sidewall portion is increased by the rubber layer. There is a problem that the ride quality is greatly impaired.

The present invention has been devised in view of the above problems, and has a novel structure different from the conventional run flat tire, that is, a bead core in which the inner surface in the tire radial direction is located near the bead bottom surface. And the tire radial direction outer surface is formed in a vertically long shape located at a height of 30 to 60% of the tire cross-sectional height, and the vertical deflection at the time of puncture while securing ride comfort during normal running is ensured. An object is to provide a run-flat tire that can be suppressed.

[0005]

The invention according to claim 1 of the present invention comprises a carcass extending from a tread portion to a bead core through a sidewall portion, and the bead core has an inner surface in a tire radial direction having a bead bottom surface. The outer surface in the tire radial direction located in the vicinity is 30 to
It is characterized by having a vertically long shape located at a height of 60%.

[0006] The bead core includes a metal layer portion in which steel wires are arranged substantially parallel to a tire circumferential direction;
It is desirable to form a laminate in which S durometer A hardness is alternately laminated in the tire radial direction with a hard rubber layer portion made of a hard rubber having a hardness of 45 to 80 degrees.

The bead core is provided with a bead apex rubber extending from the outer surface of the bead apex in a radial direction of the tire, and the bead apex rubber has a JIS durometer having a substantially semicircular shape convex outward in the tire radial direction in a tire meridian section. It can include a semicircular base made of hard rubber having an A hardness of 65 to 75 degrees.

[0008] Further, the sidewall portion is at least radially inward and outward from the outer surface of the bead core in the tire radial direction.
It is desirable to arrange a reinforcing cord layer made of a steel cord extending in the tire radial direction in the range of mm.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a run-flat tire (hereinafter sometimes simply referred to as “tire”) 1 of the present embodiment.
Is a cross-sectional view showing a no-load state in which the rim is assembled to a normal rim j and filled with a normal internal pressure, and FIG. 2 is a cross-sectional view showing the puncture running state. Here, the normal rim and the normal internal pressure are determined by the rim and the internal pressure specified for each tire in the standard system including the standard based on the tire in principle. The recommended value of the seller is adopted. In the figure, a tire 1 of the present embodiment includes a carcass 6 extending from a tread portion 2 to a bead core 5 via a sidewall portion 3 and a belt layer 7 disposed radially outside the carcass 6 and inside the tread portion 2. And

The carcass 6 is composed of at least one carcass ply 6A having a radial structure in which carcass cords are arranged at an angle of, for example, 75 to 90 degrees with respect to the tire equator C, in this embodiment, one carcass ply 6A. The carcass cord,
In this example, a polyester cord is used, but other than this, an organic fiber cord such as nylon, rayon, or aramid, or a steel cord may be used if necessary. Also,
The carcass ply 6A includes a main body 6a extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and the bead core 5 extending from the main body portion 6a.
And a turn-back portion 6b turned from the inside to the outside in the tire axial direction.

The belt layer 7 has at least two belt cords arranged at a small angle of, for example, 10 to 45 ° with respect to the tire equator, in this example, in the tire radial direction.
The two outer belt plies 7A and 7B are configured to overlap in a direction in which the cords cross each other. The belt ply 7A in the tire radial direction is formed wider than the outer belt ply 7B. Although the belt cord employs a steel cord in the present embodiment, a highly elastic organic fiber cord such as aramid or rayon may be used as necessary.

In this embodiment, the bead core 5
Is a vertically elongated tire whose inner surface 5i in the tire radial direction is located near the bead bottom surface 4b and whose outer surface 5o in the tire radial direction is located at a height h of 30 to 60% of the tire sectional height H from the bead base line BL. Is one of the features. As in the puncture running state shown in FIG. 2, such a vertically long bead core 5 can limit the longitudinal bending of the tire and support the load of the tire. Also tread part 2
Are bent inward in the tire radial direction and fit between the bead cores 5 and 5 (only one is shown in the figure), thereby preventing the bead cores 5 from moving inward in the tire axial direction and disengaging the rim. Can be effectively prevented. The toe end 4Be of the inner surface 5i and the bead bottom surface 4b.
Is set to, for example, about 3 to 20 mm.

The tire 1 of the present embodiment does not include a conventional rubber layer having a substantially crescent-shaped cross section inside the sidewall portion 3. Therefore, when a standard internal pressure is satisfied in the tire, the bead core 5
A flexible bending region can be secured in a region radially outside of the tire, and deterioration of riding comfort can be prevented.

Here, if the height h of the outer surface 5o of the bead core 5 is less than 30% of the tire sectional height H, the amount of vertical deflection at the time of puncturing becomes large, and the effective turning radius of the tire becomes small. There is a tendency not to be obtained, conversely if it exceeds 60%,
The bending area of the sidewall portion 3 formed outside the bead core 5 in the tire radial direction is reduced, and the riding comfort during normal running tends to be reduced. From such a viewpoint, it is particularly desirable that the height h of the outer surface 5o of the bead core 5 be 30 to 60%, more preferably 40 to 60%, of the tire sectional height H.

As shown in FIG. 3, the bead core 5 of the present embodiment includes a metal layer 5a in which steel wires 10 are arranged substantially parallel to the tire circumferential direction, and a metal layer 5a.
This figure illustrates an example in which a hard rubber layer portion 5b made of hard rubber having an IS durometer A hardness of 45 to 80 degrees is alternately stacked in the tire radial direction. As a result, a slight deformation in the tire radial direction or the tire axial direction can be ensured in the hard rubber layer portion 5b, and the impact on the riding comfort during puncture running can be reduced while preventing the rim assembling property from being significantly deteriorated. You can also plan. The metal layer portion 5a may use a metal cord (stranded wire) instead of the steel wire.

In such a bead core 5, when the thickness k of the hard rubber layer portion 5b in the tire radial direction is too large, the rigidity of the bead core 5 is reduced, and sufficient run-flat running performance tends not to be obtained. On the contrary, if it is too small, the rim composition tends to decrease. From such a viewpoint, the thickness k of the hard rubber layer portion 5b is, for example, 50 to 200% of the wire diameter d of the steel strand 10, and more preferably 80%.
It is desirably about 120%.

As shown in FIG. 1, a bead apex rubber 8 is provided on the outer surface 5o of the bead core 5 so as to extend radially outward from the outer surface 5o in the tire direction. In this example, the bead apex rubber 8 has a semicircular base 8a made of a hard rubber with a JIS durometer A hardness of 65 to 75 degrees and a substantially semicircular shape that protrudes outward in the tire radial direction in the tire meridian section. A triangular portion 8b arranged radially outside the tire and having a substantially triangular cross section is exemplified. The triangular portion 8b has a smaller rubber hardness than the semicircular base portion 8a, specifically, a JIS durometer A hardness of 40 to 70 degrees, more preferably 50 to 60 degrees.
Made of soft rubber. By providing the substantially semicircular base portion 8a and the triangular portion 8b whose rubber hardness is regulated in this way, the carcass 6 can be smoothly bent along the outer surface of the bead apex rubber 8 at the time of puncturing. In addition, excessive bending of the carcass cord can be prevented. This is preferable in that breakage of the carcass cord during puncturing is suppressed for a long time. The triangular portion may be omitted.

In the present embodiment, the side wall portion 3 is provided with a reinforcing cord layer 9 extending in the tire radial direction at least in a range Y of 30 mm from the outer surface 5o of the bead core 5 to the inner and outer sides in the tire radial direction. are doing. The reinforcing cord layer 9 of the present embodiment is exemplified by a steel cord ply 9a, 9b which is disposed outside the carcass 6 in the tire axial direction and overlaps inside and outside the tire axial direction. The steel cord plies 9a and 9b are
For example, the cord angle is set to 5 to 8 with respect to the tire radial direction.
The angle is set to 5 degrees, more preferably 15 to 75 degrees, and the steel cords are arranged so as to intersect each other between the plies.

Generally, a rigidity step is generated near the outer surface 5o of the bead core 5, so that the tire becomes severely bent in the puncture running state shown in FIG. By arranging such a reinforcing cord layer 9 in the range Y, local bending can be suppressed, and large heat generation due to strain can be effectively suppressed. Further, as shown in FIG. 2, the sidewall portion 3 is bent near the outer end of the bead core 5 or the bead apex rubber 8 and the outer surface thereof can be in contact with the road surface, but the reinforcing cord layer 9 is provided in the region Y as described above. In this way, the contact portion can be effectively reinforced by the steel cord, which also contributes to increasing the running distance of the run flat.

When the region Y does not cover at least a range Y of 30 mm in the radial direction of the tire from the outer surface 5o of the bead core 5, local deformation near the outer surface of the bead core 5 tends to occur. Particularly preferably,
The reinforcing cord layer 9 is preferably provided so as to cover a range of 40 mm, more preferably 50 mm, from the outer surface 5o to the inner and outer sides in the tire radial direction. Further, instead of the steel cord, a highly elastic organic fiber cord such as rayon or aramid may be employed.

[0021]

As described above, in the run-flat tire according to the present invention, the bead core has an inner surface in the tire radial direction located near the bead bottom surface and an outer surface in the tire radial direction having a tire sectional height of 30 to 60. %, When the internal pressure of the tire is reduced, the elongated bead core can support the load and limit the longitudinal bending of the tire. In addition, such a vertically long bead core utilizes the bending of the tread portion in the tire radial direction due to a decrease in internal pressure, and the tread portion is interposed between the bead cores, whereby the bead core moves on the rim inward in the tire axial direction. The rim can be prevented from coming off.

[Brief description of the drawings]

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

FIG. 2 is a left half sectional view showing the puncture traveling state.

FIG. 3 is a partially enlarged cross-sectional view of a bead core.

[Explanation of symbols]

 2 Tread portion 3 Side wall portion 4 Bead portion 5 Bead core 5i Inner surface of bead core 5o Outer surface of bead core 5a Metal layer portion 5b Hard rubber layer portion 6 Carcass 6A Carcass ply 6a Carcass ply body portion 6b Carcass ply turnback portion 7 Belt layer H Tire section height

Claims (4)

[Claims] 1. A tire having a carcass extending from a tread portion to a bead core through a sidewall portion, wherein the bead core has an inner surface in a tire radial direction near a bead bottom surface and an outer surface in a tire radial direction having a tire sectional height. A run flat tire having a vertically long shape positioned at a height of 30 to 60%. 2. The bead core comprises: a metal layer portion in which steel wires are arranged substantially parallel to a tire circumferential direction; and a hard rubber layer portion made of hard rubber having a JIS durometer A hardness of 45 to 80 degrees. The run-flat tire according to claim 1, comprising a laminated body alternately laminated in a tire radial direction. 3. An outer surface of the bead core is provided with a bead apex rubber extending radially outward from the outer surface of the bead core, and the bead apex rubber has a substantially semicircular shape which is convex outward in the tire radial direction in a tire meridian cross section. The run-flat tire according to claim 1 or 2, further comprising a semi-circular base made of hard rubber having a hardness of 65 to 75 degrees according to JIS durometer A. 4. A reinforcing cord layer made of a steel cord extending in a tire radial direction is arranged in the sidewall portion at least within a range of 30 mm inward and outward in the tire radial direction from the outer surface of the bead core. 4. The run-flat tire according to any one of claims 3 to 3.