JP2003154821A - Run-flat tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a run-flat tire that excels in durability at run-flat travel. SOLUTION: The run-flat tire comprises a main belt 8 composed of at least two bias belt layers 7a and 7b having parallel arrangements of cords extending in a bias relation to a tire center plane E on an outer circumference side of a crown portion 6 of a carcass 5, a tread part 9 reinforced by the main belt 8, buttress parts 11 positioned at both ends of the tread part 9, sidewall parts 12 interconnecting the buttress part 11 and a bead part 2, and reinforcing rubber layers 13 arranged on an inner side of the carcass 5 at least along the sidewall part 12, composed of relatively hard rubber and having a substantially crescent sectional form. A ringed flexion-suppressing reinforcing layer 14 extending along the same circumference is arranged on an outer circumference of the carcass 5 at least along the buttress part 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called side-reinforcement type run-flat tire capable of run-flat running when an abnormal decrease in tire internal pressure or puncture occurs. Improves durability during flat driving.

[0002]

2. Description of the Related Art Tires that are capable of traveling over a certain distance even when the tire internal pressure is abnormally lowered or punctured, so-called run-flat tires, have been proposed as many summer tires or the like that travel on ordinary pavement surfaces. There are two types.

The first type of run-flat tire is a so-called core type run-flat tire in which a support is built in a rim-assembled tire, and the support is provided only when the internal pressure is abnormally reduced or punctured. The tire is configured so that it can be brought into contact with the inner surface of the tire so that the crushed tire can be supported from the inner surface side thereof, which enables run-flat traveling.

However, in such a run-flat tire, a support must be incorporated at the time of assembling the rim of the tire, so that there is a problem that the workability of assembling the rim is poor and the weight and the cost are increased. There are also problems such as complexity.

The second type run-flat tire is a so-called side-reinforcement type run-flat tire in which a reinforcing rubber layer made of relatively hard rubber is disposed at least on the inner surface side of the carcass located in the sidewall portion. It is a tire, and when the internal pressure is abnormally reduced or punctured, the side wall portions reinforced by the reinforcing rubber layer are less likely to be deformed and the load is supported by these side wall portions, which enables run flat traveling. It is a thing.

In the side-reinforcement type runflat tire, since the tire portion extending from the bead portion to the sidewall portion is sufficiently reinforced by the arrangement of the reinforcing rubber layer, even when the tire is runflat, the tire portion can be Although the failure is unlikely to occur, the air inside the tire is almost exhausted during run-flat driving, so the tread portion cannot be supported from the inside, and the central area 102 of the tread portion 101 rises as shown in FIG. Buckling phenomenon is likely to occur, and the tread portion 10
The load concentrates on both side areas 103 of 1 to increase the ground contact pressure, and a part of the buttress 104 also contacts the ground.

However, in such a run flat tire, the buttress portion 104 is not particularly reinforced, so that
Compared to the tire portion such as the sidewall portion 105 and the tread portion 101, the rigidity is small and it is easily deformed,
For this reason, the buttress section 104 is
By repeatedly undergoing a large bending deformation such as bending, a crack is likely to be generated on the surface of the rubber forming the buttress portion 104, the crack progresses to the inside, and finally reaches the carcass 106 to break the cord. It may cause a failure such as.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a side-reinforcement type runflat tire having improved durability by suppressing deformation of the buttress portion during runflat running. .

[0009]

In order to achieve the above object, the present invention provides a carcass comprising at least one ply having cords arranged substantially radially between bead cores embedded in a pair of bead portions. A main belt composed of at least two inclined belt layers in which cords extending obliquely with respect to the tire equatorial plane are arranged in parallel on the outer peripheral side of the crown portion of the carcass; a tread portion reinforced by the main belt; Buttress portions located at both ends, a sidewall portion connecting between the buttress portion and the bead portion, and disposed at least on the inner surface side of the carcass over the sidewall portion, made of relatively hard rubber, and having a substantially crescent-shaped cross section. In a run flat tire including a reinforcing rubber layer having a shape, a carcass of at least a bad dress portion is formed. On the peripheral surface, it is a run-flat tire characterized by disposing a ring-shaped bent suppressing reinforcing layer extending along on the same circumference.

Further, in the bending suppression reinforcing layer, the outer end position in the tire radial direction is directly below the end part of the main belt, and the inner end position in the tire radial direction is a distance of 5 to 50% of the tire cross-sectional height. It is preferably located radially inward from the radially outer end position.

Further, the bending suppression reinforcing layer is a rubber layer made of a relatively hard rubber having a modulus of 5 MPa or more at 300% elongation, or a cord layer in which a cord having a modulus of 2000 MPa or more is covered with rubber. In addition, in the latter case, in addition, in the latter case, the cord constituting the cord layer is one or more selected from aramid fiber, nylon fiber, polyethylene terephthalate fiber, and polyethylene naphthalate fiber. More preferably, it is composed of the organic fiber cord of

Furthermore, it is preferable that the cords forming the cord layer are arranged at a relatively large angle with respect to the cords of the plies forming the carcass.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a typical half cross section in the width direction of a run flat tire according to the present invention.

The tire 1 shown in FIG. 1 has a substantially radial arrangement between bead cores 3 embedded in a pair of bead portions 2 (specifically, arranged at an angle of 70 to 90 ° with respect to the tire equatorial plane E). 1 has at least one ply having a cord, and in FIG. 1, one ply has a carcass 5 formed by folding back from the inside to the outside around the bead core 3 and the bead filler 4.

The tire 1 has at least two inclined belt layers, in which cords extending obliquely with respect to the tire equatorial plane E are arranged in parallel on the outer peripheral side of the crown portion 6 of the carcass 5, that is, two layers in FIG. A tread portion 9 reinforced by a main belt 8 composed of inclined belt layers 7a and 7b is arranged.

The main belt 8 is a crossed belt in which at least two tilted belt layers 7a and 7b of the tilted belt layers constituting the main belt 8 are laminated so that the cords cross each other with the tire equatorial plane E interposed therebetween. Preferably.

Although not shown, the tread portion 9 has a plurality of circumferential grooves extending along the tire circumferential direction and / or extending in a direction crossing the circumferential grooves, although not shown. Tread grooves such as a plurality of transverse grooves, and a plurality of sipes are appropriately arranged according to the application.

Further, in FIG. 1, a cap layer 10 in which cords are arranged substantially in parallel with the tire equatorial plane E is provided between the main belt 8 and the tread portion 9 so as to cover almost the entire width of the main belt 8. In this case, the cap layer 10 can be appropriately provided if necessary.

Buttress portions 11 are provided at both ends of the tread portion 9.
And a side wall portion 12 for connecting them is provided between the buttress portion 11 and the bead portion 2.

Further, at least on the inner surface side of the carcass 5 extending over the side wall portion 12, a reinforcing rubber layer 13 made of relatively hard rubber and having a substantially crescent-shaped cross section is disposed, which is a so-called side reinforcing type. It has a run-flat tire structure.

The main structural features of the present invention are as follows.
It is to reinforce the buttress portion 11, and more specifically, at least on the outer peripheral surface of the carcass 5 extending over the paddle portion 11,
Ring-shaped bending suppression reinforcing layer 14 extending along the same circumference
By adopting this configuration, it is possible to dramatically improve the durability of the tire during run-flat traveling, particularly the durability of the buttress portion.

More specifically, in the conventional side-reinforcement type run flat tire, the buttress portion is not particularly reinforced, so that the buttress portion 104 is bent as shown in FIG. Buttress part 104
A crack is easily generated on the surface of the rubber that constitutes the carcass, and the crack propagates to the inside, and finally the carcass 106
In some cases, a cord breakage or other failure occurred.

On the other hand, in the run-flat tire 1 of the present invention, a ring-shaped bending suppression reinforcing layer 14 extending along the same circumference is provided on the outer peripheral surface of the carcass 5 extending at least over the paddle portion 11. Thereby, since the rigidity of the buttress portion 11 is increased, the buttress portion is less likely to bend even during run flat traveling, and as a result,
Since it is possible to suppress the generation of cracks on the surface of the rubber that constitutes the buttress portion, the durability of the buttress is improved, which in turn makes it possible to improve the durability of the tire as a whole.

As shown in FIG. 1, the bending suppression reinforcing layer 14 is
The tire radial outer end position 15 is directly below the end portion of the main belt 8, and the tire radial inner end position 16 is 5 of the tire cross-section height H.
It is preferable that the distance from the outer end position 15 in the tire radial direction is inward in the tire radial direction by a distance of -50% in order to effectively improve durability.

In order to ensure durability, the bending suppression reinforcing layer 14 is a rubber layer made of rubber having a modulus at 300% elongation of 5 MPa or more, and a cord having a modulus of 2000 MPa or more is covered with rubber. It is preferably a code layer. The value of modulus at 300% elongation (tensile stress (MPa) at 300% elongation) was measured according to JIS K 6251-1993 using JIS dumbbell No. 3 test piece at a test temperature of 25 ° C. The value of the modulus of the cord was measured according to JIS L 1017-1983 at a test temperature of 25 ° C. and a speed of 30 cm / min, gripping interval: The value when initial tension is performed at 250 mm.

When the bending suppression reinforcing layer 14 is composed of a cord layer, the cord constituting the cord layer is selected from aramid fiber, nylon fiber, polyethylene terephthalate fiber, and polyethylene naphthalate fiber. It is preferably composed of a cord of one kind or two or more kinds of organic fibers.

Further, when the cords forming the bending suppression reinforcing layer 14 are arranged within a relatively small angle range (particularly preferably 0 °) with respect to the cords of the plies forming the carcass 5, the bending suppression is suppressed. The rigidity of the entire buttress portion can be increased by an amount corresponding to the increase in the bending rigidity of the cord of the reinforcing layer 14, which improves the durability of the tire.

However, the cord forming the bending suppression reinforcing layer 14 has a relatively large angle (preferably 45 to 90 °, particularly preferable) with respect to the cord of the ply forming the carcass 5.
90 °), a shearing force is generated between the cord of the bending suppression reinforcing layer 14 and the ply cord, and the bending suppression reinforcing layer 14
As a result of effectively suppressing the expansion (diameter expansion) of the ply portion located on the inner surface side of the tire, the bending deformation of the buttress portion during run-flat traveling becomes small, and the durability of the tire can be further improved. Therefore, it is preferable to dispose the bending suppression reinforcing layer 14 at such a cord angle.

Although the bending suppression reinforcing layer 14 is shown in FIG. 1 as having one layer, it may be provided in two or more layers if necessary, and in the case of two or more layers, It may be composed of a composite layer of the rubber layer and the cord layer.

The above is merely an example of the embodiment of the present invention, and various modifications can be made within the scope of the claims.

[0031]

EXAMPLES Next, run-flat tires according to the present invention were prototyped and their performances were evaluated, which will be described below. Example 1 The tire of Example 1 is a run-flat tire having a tire width direction cross section shown in FIG. 1 and a tire size of 155 / 65R13, and a radial consisting of one ply in which cords are radially arranged. A reinforcing rubber layer 13 was provided on the inner surface side of the carcass 5, and on the outer peripheral surface of the radial carcass 5 over the paddle portion 11, a bending suppression reinforcing layer 14 consisting of a single cord layer coated with nylon cord was arranged. In the bending suppression reinforcing layer 14, the tire radial direction outer end position 15 is directly below the end portion of the main belt 8, and the tire radial direction inner end position 16 is from the tire radial direction outer end position 15 to the tire radial direction inward direction. The nylon cord of the bending suppression reinforcing layer 14 had a modulus of 2500 MPa and was arranged at an angle of 90 ° with respect to the cord of the radial carcass 5, measured at 10% of the tire section height H.
Other tire structures were the same as those of a general pneumatic radial tire.

Example 2 The tire of Example 2 is almost the same as the tire of Example 1 except that the bending suppression reinforcing layer 14 is a rubber layer made of rubber having a modulus at 300% elongation of 6 MPa. It has a similar structure.

Example 3 The tire of Example 3 is almost the same as the tire of Example 1 except that the bending suppression reinforcing layer 14 is a rubber layer made of rubber having a modulus at 300% elongation of 4 MPa. It has a similar structure.

Conventional Example The conventional tire has substantially the same structure as the tire of Example 1 except that the bending suppression reinforcing layer is not provided.

(Performance Evaluation) For each of the above-mentioned test tires,
The durability during run-flat traveling was evaluated and will be described below.

Durability during run-flat running is as follows. After mounting the above-mentioned test tire on a standard rim (4.50B), these tires were mounted on an actual vehicle, and the relative internal pressure of the tire was measured only for the tire mounted on the front right side. After the pressure was set to 0 kPa, the vehicle was run at 90 km / h, the running distance until the tire mounted on the front right side was damaged, and the measured value was evaluated. Table 1 shows the evaluation results. still,
The numerical values shown in Table 1 are shown as index ratios when the conventional example is 100, and the larger the numerical value, the better the durability during run-flat running.

[0037]

[Table 1]

From the evaluation results shown in Table 1, all of Examples 1 to 3 are far superior in durability during run-flat traveling as compared with the conventional example.

[0039]

According to the present invention, by reinforcing the buttress portion by disposing the bending suppressing reinforcing layer, it becomes possible to provide a run flat tire having excellent durability during run flat running.

[Brief description of drawings]

FIG. 1 is a widthwise half cross-sectional view of a typical run flat tire according to the present invention.

FIG. 2 is a diagram for explaining a state when a conventional run-flat tire is run flat.

[Explanation of symbols]

1 run flat tire 2 bead part 3 bead core 4 bead filler 5 carcass 6 Crown part 7a, 7b inclined belt layer 8 main belt 9 tread section 10 cap layer 11 Buttress Department 12 Side wall part 13 Reinforced rubber layer 14 Bending suppression reinforcement layer 15 Tire radial outer end position of bending suppression reinforcement layer 16 Inner end position in the tire radial direction of the bending suppression reinforcement layer E tire equatorial plane H Tire cross section height

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Claims (6)

[Claims] 1. A carcass consisting of at least one ply having cords arranged substantially radially between bead cores embedded in a pair of bead parts, and a carcass crown part outer peripheral side with respect to a tire equatorial plane. A main belt composed of at least two inclined belt layers in which cords extending obliquely are arranged in parallel, a tread portion reinforced by the main belt, buttress portions located at both end portions of the tread portion, and a buttress portion and a bead portion. In a run flat tire, which includes a sidewall portion connecting between the two and at least an inner surface side of the carcass that extends over the sidewall portion, is made of relatively hard rubber, and has a reinforcing rubber layer having a substantially crescent-shaped cross-sectional shape, A ring-shaped bend extending along the same circumference on the outer peripheral surface of the carcass that extends at least over the baddres. A run-flat tire having a bending suppression reinforcing layer. 2. The bending suppression reinforcing layer has an outer end position in the tire radial direction immediately below an end of the main belt, and an inner end position in the tire radial direction at a distance of 5 to 50% of a tire cross-sectional height. The run flat tire according to claim 1, which is located radially inward from the radially outer end position. 3. The run-flat tire according to claim 1, wherein the bending suppression reinforcing layer is a rubber layer made of a relatively hard rubber having a modulus at 300% elongation of 5 MPa or more. 4. The flexure suppressing reinforcing layer has a modulus of 2000 MP.
The run flat tire according to claim 1 or 2, which is a cord layer in which a cord of a or more is coated with rubber. 5. The cord constituting the cord layer comprises a cord of one or more kinds of organic fibers selected from aramid fiber, nylon fiber, polyethylene terephthalate fiber, and polyethylene naphthalate fiber. Run flat tires listed. 6. The run flat tire according to claim 4, wherein the cords forming the cord layer are arranged at a relatively large angle with respect to the cords of the plies forming the carcass.